


the scientific method

by iroirong



Category: Batman - All Media Types
Genre: 5+1 Things, Duke Thomas is Signal, Duke Thomas is a Batfamily Member, Duke Thomas-centric, Gen, Physics, Science Experiments, Sibling Bonding, duke: wow why is my new family so big, lots of creative license on the physics tbh, me tagging all the relationships: YEAH WHY IS YOUR NEW FAMILY SO FUCKING BIG, through loving experimentation on your metahuman sibling.
Language: English
Status: Completed
Published: 2020-12-31
Updated: 2021-01-06
Packaged: 2021-03-09 21:01:55
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 6
Words: 20,790
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27522724
Author URL: https://archiveofourown.org/users/iroirong/pseuds/iroirong
Summary: 5 stupid ways Duke's siblings discovered how his powers worked, and 1 time he figured it out for himself."You have no idea," Dick said. "I had to live through all of their teenage years. They were each independently obsessed with Mythbusters at separate points in their life. I'm pretty sure Cass and Tim have wanted a meta to experiment on since they were 14, but Bruce always said no."
Relationships: Cassandra Cain & Duke Thomas, Dick Grayson & Duke Thomas, Duke Thomas & Bruce Wayne, Duke Thomas & Damian Wayne, Duke Thomas & Jason Todd, Stephanie Brown & Duke Thomas, Stephanie Brown/Cassandra Cain, Tim Drake & Duke Thomas
Comments: 122
Kudos: 612





	1. 380-700nm

**Notes for the Chapter:**

> batcest shippers please dni

It was a surprisingly quiet morning in the Manor when Duke stumbled downstairs, bleary-eyed and with a slight crick in his neck from sleeping at a wrong angle. He had a low-grade dehydration headache and his toes were cold on the hardwood floor, and he was too preoccupied with wondering about what he'd do for the English essay he procrastinated on to fully realize that the house was suspiciously silent for nine in the morning on a weekend.

He stopped on the bottom stair, foot frozen in descent, as it hit him that there was no audible chaos in any part of the house.

"Guys?" Duke called into the emptiness. He heard a slight shuffle down the hall on the way to the kitchen and went to investigate, like a good little detective.

"Oh, Master Duke," Alfred responded, his head stuck halfway in the hallway closet he was rummaging through. "Could you fetch the biscuit tin for me?"

Duke took a second to translate in his head before heading for the blue box of Danish cookies on the counter. 

"This one?" he asked. 

"The very same," Alfred confirmed, straightening up. He walked past Duke, who took it as an unspoken _'follow me'_ and trotted after the older man, clutching the metal box in hand.

"Your brothers should already be waiting," Alfred said, walking into the study. Duke glanced at the grandfather clock before looking back at Alfred.

"Waiting for what?" He asked. The nervousness came back; ever since he'd come to live at the Manor, he'd felt off-balance, off-kilter, and always terrified that he'd missed something absolutely vital. Alfred remained calm and placid, however, which was reassuring. If it was life-or-death, Duke wasn't sure the stiff upper lip would break, but he'd probably be told to hurry at the very least.

"Maintenence," Alfred said, each syllable crisply enunciated in a delivery so dry, it could be packaged and sold as an alternative to silica gel. "Though, Master Jason has a few alternate suggestions on naming."

"Uh," Duke said eloquently, glancing back down at the cookies in his hands. "Okay." That had cleared precisely nothing up for him, but these people insisted on some kind of cloak-and-dagger super-spy euphemism for everything, and, in his experience, it was best to just go in headfirst and figure out what they meant on the way.

"Go on down," Alfred said, turning to head back to the kitchen. "I will come down shortly with refreshments."

"Sure," said Duke, wondering if "refreshments" was code for some kind of Bat-gadget or if he was just talking about the kettle on the stove. He shrugged and walked down into the damp cave, wishing he'd thought to pull a hoodie on before he got out of bed. Or, at the very least, some socks.

He stopped at the entrance and surveyed his foster brothers all arranged in a circle, their costumes splayed out in front of them, and all arguing with each other, probably lightheartedly. His foster dad was chugging a mug of coffee and making eye contact with none of them.

"Welcome," Jason said from his spot in the circle, "to Stitch 'n' Bitch."

"I keep telling you," Tim said, "that's for knitting, not darning."

"Darning," Damian repeated mockingly, his nose scrunched up. Damian, Duke noted, was also carefully placed between Dick and Bruce and as physically distant from Tim as possible. He figured that was smart of them.

"Someday," Dick said, "I'm gonna knit Jason a sweater, just so you can't say that anymore."

"Would he even wear it?" Tim asked.

  
  
"Depends," Jason said. "How good are you at knitting?"

"Eh, I'm a 4 out of 10. Bet I could get your bat symbol into the pattern, though."

"Duke," Bruce said, finishing his coffee and setting his mug aside. "Glad you could join us."

"Yeah," Duke said slowly. "Sure. I brought, uh, Alfred told me to bring this?" He held up the cookie tin and belatedly realized that the things sliding around in the metal box were clearly too small and metallic to be cookies.

"Yes, thank you," Bruce said. "Take a seat, your costume is next to Tim."

"And ignore Damian," Tim said, "he gets cranky when he stays up too long."

Damian let out an outraged screech, not unlike a suddenly and abruptly soaked cat, which was enough warning for Bruce to reach around and grab him firmly. Meanwhile, Duke gingerly set himself down between Tim and Jason, picking up his costume and fingering at the hole that some whackjob had left in his costume after coming for him with a knife. Which was the sort of thing he'd never had to worry about before he'd decided vigilantism was a good idea, but, no use considering a career change now.

Jason and Dick, clearly, had been continuing their conversation.

"But Jay," Dick said, voice going mocking-sincere, "I worry about you, out there alone in those cold, cold, Gotham nights!"

"Jackass," Jason said, shoving him in the shoulder as Dick's act cracked and he started laughing. "I swear to god, if I wake up on Christmas or Chanukah and you hand me a _hand-made sweater_ -"

"Well," Dick said, "now I have to."

"I think it's time we get started," Bruce said, his voice heavy and tired and his arm still wrapped around a surly pre-teen. Duke resisted the urge to point out that the only reason any of them were foster brothers was because Bruce literally signed up for this, since that seemed a little mean.

Bruce held out his hand for the cookie tin and Duke leaned forward to hand it to him. He cracked open the lid to reveal the sewing supplies inside, which, in hindsight, made perfect sense to Duke. After taking out a sewing needle and some thread, Bruce handed the tin clockwise to Tim, who pulled his own needle and thread out and gave it over to Duke.

"Is your costume made from Kevlar weave?" Tim asked as he passed the box over.

"Yeah," Duke said, because that sounded right. "I think."

"Here," Tim said, fishing through the box to pull out a roll of pale yellow thread. "You'll want to use the Para-Aramid thread, the other kinds don't have the tensile strength."

Duke hesitantly took it, passing the box on to Jason. "Thanks," he said.

"No problem," Tim replied, hunched over and threading his needle.

"Ask him about the P-A threads," Dick called, reaching over to grab his own. "He's been helping Fox make 'em."

Tim blushed a little, which took Duke completely aback. "Helping is a bit of a strong word for it," Tim said.

Bruce looked up. "Did your experiments with the meta-aramides succeed?" he asked, and then they were off talking about chemistry at a level that Duke, who had a public high school education and then two months of crash-course bat-education, couldn't quite grasp yet.

"Don't worry," Dick said as he rewired something in his gauntlets. "The rest of us can never figure out what they're talking about either."

"Speak for yourself," Damian muttered, sewing another straight running stitch into the tear in his hood. "I grasp it all perfectly fine."

"Good job on that one," Dick said. "I think your backstitch is improving."

"Don't condescend to me," Damian said, clearly pleased with the praise.

"I'm not!" Dick said. "It's really good now."

Duke watched Damian's next few movements very carefully before copying; Alfred had at some point a few months ago taught him the basics, but only on normal clothes. His Signal costume was rougher, with more layers of Kevlar weave to get through with the needle, and Duke was worried with each pass of the needle that he'd mess it up a little beyond repair. It was dumb, because this costume could literally stop bullets, but it was also not dumb, because this costume was the only thing standing _between_ him and a bullet.

After half hour of silent work, Duke had begun to relax. He had even felt a little more comfortable, here with the members of his new family, taking part in what was clearly a family ritual/sibling bonding exercise/logistical challenge for a superhero household. Duke had felt slightly out of lockstep before for reasons he couldn't even begin to explain -- there was something just uncomfortable about standing around his foster brothers, all of whom had relationships and trauma with each other that he simply did not figure into. He often felt like a guest in the house, even now, months after his legal fostering. But for this one Sunday morning, down in the cave, his fingers and feet freezing as he sat on the hard rock ground of the cave sewing in a hunched position that made the crick in his neck that much worse, he felt a little like he really was part of something bigger. Like he really could claim to be one of them.

Naturally, this is when it went sideways.

"Can you pass me some of the red," Tim asked, glancing over at the box. It was stretched in front of Jason, who was taking a very tiny screwdriver to his helmet.

"Yeah, sure," Jason said, fishing a spool of thread out without looking and tossing it over. Tim caught it and then brought it closer to his vision.

"Jason, this is your thread."

"What?" Jason asked, still distracted. Dick paused from where he was showing Damian his wrist gauntlet's inner workings, looking over.

"The thread. This formulation's for your suit, not mine. Mine's the other red thread."

Jason finally looked up, furrowing his brow. He leaned forward and rummaged in the metal box, coming up with another spool of thread, also in red.

"Tim," Jason said. "Is your costume seriously the same shade of red as mine?"

"Well," Tim said, "It'd make sense. Technically, it's your suit originally."

"I cannot believe you just took the same shade of red as my costume and called it a day," Jason said, shaking his head. "Red Robin. Oh my god."

"Drake certainly doesn't win points for originality," Damian sniped.

"Shut up, you're like, the fourth Robin."

"Fifth," Bruce corrected, then refused to elaborate. Duke wondered briefly if he counted, then discarded that thought because, no, he did not want to be sixth. He held the Signal costume a little closer and squinted at Tim's Red Robin costume, then Jason's in turn.

"Hang on," he said. "Those aren't the same shade at all."

Everyone turned to him at once. It was the slightest bit unnerving.

"What are you talking about?" Damian demanded.

"They look pretty similar to me," Dick said, "but the lighting here always sucks. 'Cause it's a literal cave."

"No," Duke insisted, looking closer and feeling even more sure of himself. "Those are definitely not the same reds. The blacks too, those are totally different colors. Tim's red is, I don't know, more loud?"

"Wait," Dick said. "What's your meta power again?"

"Holy shit," Tim said, catching on. "You can see outside the visible light spectrum."

"What?" Duke asked, very caught off guard.

"I think you're seeing infrared on my costume," Tim said.

"Wait, you see more colors than the rest of us?" Jason asked. "What does infrared look like?"

"Uh," Duke said, because well, how would you explain what red looks like to someone blind from birth? "It just, looks like that?"

"Wait here," Tim said, rushing off. Bruce watched as he ran for the chemical storeroom with a weary sigh.

"Huh," said Dick to a blinking Duke. "You're like a mantis shrimp."  
  


"What?" Duke said, surrendering to his bewilderment.

"You know, mantis shrimp? Four times as many photoreceptors as humans, so they see a bunch of different colors that we can't."

"Flattering comparison," Duke said. Jason snorted.

"What does black look like to you?" Damian asked, a hint of real curiosity in his voice, hidden mostly by his scowl.

"Uh," Duke stalled, his eyes landing, naturally, on Bruce. "Like a bunch of different colors at once. Kinda like… they all run together, like an oil spill. If I tilt my head in one direction, it looks totally different than from another direction."

Bruce nodded, encouragingly. "All black? Is it different on surfaces or on shadows?"

"Shadows are different," Duke agreed. "They're more uniform colors."

Tim, out of breath, came running back to the circle with ziploc bags of white powders grasped in his hands.

"What colors are these?" He asked.

"White?" Duke responded, feeling uncomfortably like this was a trick question.

"Are they the same white?" Tim asked, undeterred.

"No?"

"Hm," everyone else hummed with the same tone and pitch. They had all clearly learned it from Bruce, but knowing that didn't make it any less freaky.

"Is it not for you?"

"I hate to break it to you," Jason said, "but there's only one white for us normal non-meta suckers."

Tim rapidly shuffled through the bags before pulling one out. "Is this white one, I mean, does this white one look red-ish to you?"

"No?" Duke said. "I don't know how to explain it. It doesn't look like red, it looks white. Just not the same white as the other ones."

Tim paused mid ziploc-bag-shuffle. He stared at Duke for just long enough for the younger boy to start feeling distinctly like a specimen about to be put under observation.

"Dad," Tim said, "is it okay if Duke and I skip out on Stitch 'n' Bitch and take a day off?"

"That's not fair," Damian said. "We all are curious."

"Hear, hear," Jason said. "This is the most fun maintenance day I've had in a year."

"You come to two of these _a_ year," Dick pointed out.

Bruce sighed heavily, ignoring his other sons. "Duke, is this okay with you?"

"Well-" Duke started.

"We'll help you figure out how your powers work better," Tim said all in a rush.

"Sibling bonding," Dick added.

Duke glanced around and felt a little like he was sealing his fate when he breathed out heavily and said: "Yeah, sure."

It wasn't too bad, though. They finally left the cave, Duke stopped back up at his room to put some socks and shoes on, and they went tromping out into the woods beyond the manor.

Damian tried to catch various lizards or bugs to see if the principle of "they have weird vision and so do you" would yield any interesting sights for Duke, while Jason was preoccupied mostly with trying to dunk Tim in the creek and asking Duke what color water looked like to him. The answer, apparently, was different from the others, though nobody could figure out how to communicate how, exactly.

Dick eventually figured out that Duke could distinguish plant species based on the color of their leaves with shocking accuracy, which lead to a scavenger hunt that eventually led to a weird hybrid game of tag and tackle football, the rules of which Duke was told he'd learn as he went. He did, several bodily flings into the dirt later, and even managed to pull one of his own on Jason.

A good day in the woods, all in all.


	2. b = L/(4π*d^2)

**Summary for the Chapter:**

> Since the area increases as the square of the distance, the brightness of the light must decrease as the inverse square of the distance. Thus, brightness follows the inverse-square law.

"You have no idea," Dick said. "I had to live through _all_ of their teenage years. They were each independently obsessed with Mythbusters at separate points in their life. I'm pretty sure Cass and Tim have wanted a meta to experiment on since they were 14, but Bruce always said no."

"Experiment on?"

"Don't worry," Jason called from the kitchen. "Tim has a Superman clone and a speedster to mess with now."

Duke looked at Dick, who was tilting his head thoughtfully. "I guess you just have to worry about Cass, then. That's not too helpful though; if she wants you, none of us can stop her."

"You can always try bargaining with her girlfriend," Jason said. He'd wandered into the living room, attracted by the sound of a younger brother's despair.

"Oh, they're officially together?" Dick asked, and Jason muttered: "Unfortunately."

"Cass is dating someone?" Duke asked. His older sister was rarely home, though when she was, she was a quiet and somewhat forbidding presence. He'd have thought she was the most like Bruce of all his adopted siblings, but most of the time he spent with her was in either Dick or Jason's apartment, and her brothers tended to bring the little gremlin out of her. He had no idea she had a girlfriend; he'd seen her sneak up behind and wet willy Tim.

"Stephanie Brown," Dick said. "AKA Spoiler. She likes calling Jason 'Edgar Allen Crow' whenever they end up working together, and it drives him insane, so he keeps hinting to Cass that he thinks they should break up."

"They should. I don't know why we all let her be the one to help Cass learn to read. She's the worst option. Doesn't even like fiction," Jason said, scandalized. "One time I asked her which her favorite Sturm un Drang work was, and she told me ' _gesundheit'_."

"Can we please go back to the experimentation thing?" Duke said, a little faintly. Dick ignored him.

"It's a good joke, though," he said. "I can appreciate that. The technical mastery over punning."

"Edgar Allen Crow," Jason muttered. "I don't even do the bird theme anymore!"

"Once a Robin," Dick said, winking at Duke, "you're always a Robin."

Duke smiled back a little hesitantly. Truth be told, he'd felt a little uncomfortable around the original Robin. Whereas hanging out with the rest of his foster family always felt just a little like he was crashing a party he wasn't explicitly invited to, talking to Dick felt like being trapped in a passive-aggressively polite conversation with the host. It didn't help that Dick was consummately cheerful in a way that was clearly not all the way real. Duke couldn't shake the way he always expected the mask to drop and the real anger to show itself.

Jason was just as hard to navigate in his own way; Bruce had days where he flatly refused to talk about his second-born, even if they were few and far between. Every time Duke looked at Jason, he thought about all he knew, the whole bloody story of Robin and the Red Hood and Robin that he'd seen first as an outsider and then through the testimonies of every person in this family except Jason himself. Duke looked at Jason and would think: I know too much about you.

Dick had turned his attention back to his first brother.

"Is the stove still running?" Dick asked, rhetorically. They could all hear the gas burner still going. "The milk'll boil over if you don't watch it."

Jason sighed, beleaguered. "I'm not making it with milk," he said, the rhythm of his voice belying that this was a well-worn argument.

Dick made a face and settled into his oppository role. "Why on earth would you make hot chocolate with _just_ water?"

"Milk's gross," Jason said. "It shouldn't be in anything."

"Baked goods," Dick volleyed back. "Ice cream. Fancy coffees. Bubble tea."

Jason shrugged. "You can't taste it in those," he argued simply.

Dick suddenly turned to face Duke. "Alright, Duke, be our tiebreaker. Hot chocolate with milk or water?"

Duke, startled to be suddenly addressed, froze. "Uh…" he said, "you can make it half and half?"

Jason raised an eyebrow and Duke winced over how wishy-washy that sounded, even before his brother said anything.

"Yeah, okay, I like it with just water," he restated. "Sorry, Dick."

"Fuck yeah," Jason said, ducking back into the kitchen. "Finally, a brother with taste."

"I would say you're dead to me," Dick said, "but Jason's already here."

Duke laughed hesitantly because he was not sure that he'd really graduated to the level of comfort where he could make jokes about his foster brother's deaths. Or rather, 'brothers' deaths'. Duke wasn't really sure he even wanted to graduate to that level.

"Yeah, yeah," Jason grumbled, hunching over a pot. "For that, you're getting the shitty thermos."

"This is my apartment," Dick said. "Those are my thermoses."

"Sucks. Duke, cupboard on your left, pick any cup except the Flash one 'cause it sucks."

Duke dutifully opened up the cupboard and located a mismatched set of thermoses, one of which was clearly the ancient and battered neon-yellow Kid Flash merchandised and branded water bottle that Jason had specified. The others were more nondescript, simple solid colors, though one at the very front had many water-damaged stickers clinging on to it. Duke pulled that one out and inspected it more closely. He had sort of expected more superhero logos, but the stickers looked like the kind you'd buy from a stationery shop. A few stylized stars in various colors, some cartoon cats, and a few cacti.

"Good choice," Dick said, near him. "That one keeps the heat in well." He reached past Duke to claim the very conspicuous yellow thermos and held it up to Duke's arm.

"Not the same yellow," he concluded, bringing the thermos over to the stove. Jason was dutifully whisking some swiss miss into the bubbling pot, the heat turned off.

"I am not pouring yours first," he said. "I do not trust the plastic on that thing to not melt into a puddle."

"Aw," Dick said. "It's tough. It'll be fine."

"Nope," Jason said, grabbing for an olive green bottle. "You are going last."

He poured out his own drink and then Duke's, and Duke swore Jason turned the thermos over just slightly in his hand and smiled at the stickers. Then, Jason moved with exaggeratedly slow movements while Dick attempted to make the nonverbal act of rolling his eyes as loud as possible. Duke grinned, taking a small sip of the piping hot cocoa. It was pretty good: no clumps, which always happened when he made it himself.

"I think it's cooled off enough; just pour the hot cocoa in and we can leave."

"I don't know," Jason said, his eyes going wide and innocent in a way that he should not have been able to pull off. "I don't think it's safe to put liquid this hot in a plastic cup."

"Jason," Dick said. "I will hit you."

"I'll spill it!"

"No, you won't," Dick said, swiping out to hit him in the shoulder. Jason moved to avoid it, and lo and behold, didn't spill any of the remaining cocoa in the pot. "I was literally there when Bruce drilled you on balancing with the water balloons."

"Yeah, yeah, give me your goddamn cup." Jason turned to Duke as he poured and said, "Don't believe anything he says, he's been an asshole older brother for ten years."

"Lies," Dick said, reclaiming his thermos. "All of them."

He winked at Duke like Duke was in on the joke, but Duke was still stuck on the phrase "older brother." That was, legally speaking, probably what Dick and Jason were to him -- or at least, he didn't know of any other simple way of explaining the intricacies of adoption and fostering law that connected them all -- but it felt almost proprietary to call either of them, out loud, "older brother." Duke felt a little jolt on envy at the ease with which Jason said the word; Jason, who should have by all rights had as much difficulty as he did calling Dick his older brother, even more, because part of those ten years was bad blood and Duke's four months had been smooth sailing so far.

He took a sip again of the cocoa Jason made for him, with water, and wondered if whoever taught Jason how to make it had also been lactose-intolerant, just like Duke's mom was. Is.

"Both of you, get your coats," Dick said from the front door, grabbing the keys off the counter.

"I'm wearing my coat, _mom,"_ Jason muttered, zipping his leather jacket up. Duke grabbed his own Gotham Knights sweatshirt off the back of the couch and tugged it on before reaching again for the same outer jacket that had served him well through the onslaught of two New Jersey winters before this one.

The three boys stepped outside past the invisible threshold of the doorway and out from the heated apartment into the freezing night air. Immediately, Duke could see his breath condensing in the air and felt the urge to shiver already. Gotham cold pierced right to the bone, and Duke could already feel his fingers and toes stiffening.

"You know," Duke said, "when I was a kid, some neighborhood kid convinced me you'd get frostbite after ten minutes outside in Gotham."

"Shit," Jason said. "I still think that."

Duke smiled briefly. Very briefly. His cheek muscles protested the movement. "How many pairs of socks are you wearing right now?"

"Three," Jason said. "Four by December though, or I will lose my toes."

"Don't worry," Dick said, locking the door behind him. "We're getting in the car."

"Man," Jason said. "Back in my day, we had to conduct all our stakeouts on a freezing cold rooftop, ankle-deep in the goddamn snow, without any fucking pants. You young'uns have no idea how good you have it."

"I think the pants thing is common sense," Duke said. 

"Hey," Dick pointed at him. "Leotards are a grand traditional costume of the Grayson family, stretching back generations, and I will not have you slandering them."

Duke had precisely four seconds to think, _"Oh no, did I just talk shit about this guy's dead family?"_ before Jason snorted.

"That's total bullshit," he said. "I've seen the posters, the leotard was just a you thing."

"Yeah," Dick admitted. "But I was eight and thought they looked cool. You were twelve. No excuse."

They argued all through their walk to the parking garage where Dick's car was, with Duke idly interjecting if he thought he had something funny enough to say, which was rare. 

They got in the car and Duke leaned his head against the window, watching out idly as they slowly drove from Dick's apartment in Thorndike, deep in Lowtown in south-west Gotham, to their destination on the east end of Midtown, the warehousing district south of Miller's Harbor. They crossed the Westbury Bridge, the black-gunk water of the Gotham Channel underneath them stinking so heavily that it filtered its way into the car, and it wasn't until they took the exit off the highway, leaving the lights of Gotham University behind them as they headed east, that Duke finally worked up the courage to ask:

"Hey, so, not that I'm not flattered that you guys asked me to hang out on your stakeout or anything, but uh, why me? You know, not to be all 'it's past my bedtime,' but this night stuff is usually you guys's thing, right? I just work the day shift."

"Well, first of all," Dick said, raising his voice to cut off whatever Jason had started to say, "you're our brother and we want to hang out with you."

"Also we wanna know how the future vision works," Jason added quickly after.

Duke shifted slightly in the backseat, a sinking feeling in his gut.

"Yeah, uh," he shifted, then remembered that the other two people in the car were detectives trained to pick up on body language and then froze in place instead. "I just, I don't really know how the future stuff works either."

He got it all out in a rush and prepared himself to be subjected to well-hidden disappointment for the rest of the car ride and the god-knows-how-long stakeout.

"That's fine," Dick said, and maybe he was a really really good actor, which was always possible. "The fun's in the discovery."

"Science, true daughter of old time thou art," Jason said, slightly under his breath and slightly far away.

"Who alterest all things with thy peering eyes," Duke finished, a little thrill in his heart, feeling half like he was intruding and taking up space and half like, well, he was finishing the refrain.

"That's Edgar Allen Poe, isn't it?" Dick asked from the driver's seat, his eyes never leaving the road. 

Duke felt his attention regardless, and with a wry smile and a stab of confidence, he said, "I thought it was Edgar Allen Crow for him?"

Jason groaned. "I just wanted one person," he said, dropping his head back and letting it thunk against the seat, "one person in this whole family who isn't like this."

"Alfred," Dick and Duke said at the same time. 

They high fived; Jason muttered something rude at Dick.

Eventually, the cleared streets of the residential district gave way to the low-slung metal shacks that Gotham called a warehouse district. Beyond it, one could possibly see the docks, great cargo ships moored overnight on their journey up and down the east coast or even out across the Atlantic. Gotham had clung to its chemical manufacturing crown through the decades of globalization and industrialism that had snatched its more respectable steel and textile mills, leaving behind only hollow, rickety skeleton plants for petrochemicals on its shores, lit up in sickly yellows.

"Did Jason tell you what we're looking for?" Dick asked, absentmindedly swirling his mug of chocolate.

"Uh, he just said it's a standard stakeout," Duke said, suddenly worried there was some sort of file he forgot to look out for that would have explained all of this for him, and now the other two would think he was dumb for not having checked.

"Yeah," Jason said. "Abandoned warehouse, looks like it's being used as a base. Don't know by who, standard stakeout rules apply."

"Except, because we're not Bruce and don't want to torture ourselves," Dick said, easing the car into parallel park on the side of the street, "we're doing it in a heated car and not a rooftop. With hot chocolate."

"You been on a lot of stakeouts yet, Duke?" Jason asked, unscrewing the top of his cup.

"Not that many," Duke said. "Didn't know it was that big a part of the job when I started We Are Robin," he said, a little twist to his mouth. "Used to think superheroes were all patrol and stopping muggings."

"Superheroes are all patrol," Dick said, grinning and taking a sip from his Flash mug. "We're just detectives, too."

"Which means we're always the ones who have to do the boring shit," Jason said. "Like spend five hours staring at a warehouse."

"Tell me about it," Dick said.

"How long will this one go?" Duke asked. 

"Probably not that long," Jason said, then gestured at the windshield. "Lights only on in the left half of the warehouse. Can't be too many of them, stands to reason that the meeting can't be too long. I give it two hours."

They were silent for a few seconds, before Dick hummed, taking a sip of his drink. "You got one?" he asked Jason.

"Yeah, go," he said.

"Is it a human man?"

"Uh," Jason shifted his mug and held his hand out flat, see-sawing it in the universal "sort of" motion. "Nineteen."

Dick was quiet for a second, while Duke furrowed his brow, trying to catch up with this new development.

"Is it from a Greek myth?" Dick asked.

"Fuck. Yes, that's eighteen."

"The minotaur," Dick said with an air of triumph.

Jason shook his head. "Man, I want a do-over. That was not fair."

"Sore loser, little wing," Dick said, reaching over to ruffle Jason's hair and getting smacked for his trouble.

"Duke," Jason said, still fending off his brother as he turned around in his seat, "feel free to cheat with the future vision. But only with him."

"No, no, if we're playing twenty questions with a clairvoyant, I think he should be allowed to kick your ass too."

"Uh, I have to concentrate for that to work," Duke said. "I can't, like, see the future right away."

Dick and Jason looked at each other for a second before both turning to him in the backseat.

"How far into the future can you usually see?" Jason asked. 

Duke blinked. "I'm not… sure? I usually see enough to stay alive in a fight."

Dick narrowed his eyes in thought. Then he turned to Jason and said, "I'm thinking of something, twenty questions." To Duke, he said: "I want to try something. Can you concentrate right now?"

"I'll try," Duke said hesitantly, and Dick nodded, a brisk motion belied by the way his eyes seemed to twinkle in curiosity and excitement.

"Is it a person?" Jason asked, while Duke, at a loss for what to do, started squinting and thinking real hard about seeing the future.

"No. Nineteen."

"Is it a place?"

"Yes. Eighteen."

"Is it in Gotham?"

"No. Seventeen."

"In the US?"

"Yes, sixteen."

And then, suddenly, with a stabbing pain and a disorienting double vision, Duke saw Jason ask, _"Is it the Daily Planet?"_ His voice was blurry, like Duke was listening with his ear pressed against a wall, and just as quickly as it came, the vision dissipated like smoke and he saw Jason open his mouth in this present time.

"Daily Planet," Duke said, cutting Jason off, and Dick turned and blinked.

"Yeah," he said with a smile. "When'd you figure that out?"

"Just now," Duke said. "I just saw Jason ask. Uh, or -- I don't know how the tenses work, but I saw him about to ask."

"Hm," Jason said. "So what was that, three seconds?"

"Three-ish, maybe four," Duke said with a shrug. "I'm not sure."

"Wait," Dick said, ducking down to grab his phone. He turned the timer on and angled the phone screen towards Duke. "Can you see that?"

"Yeah," Duke said, shifting up. He was seated directly behind Dick, so Dick had to hold the phone above his head, the LED screen glowing blue in the dark car. 

"Set the stopwatch for me, let's go again."

"I got one," Jason said as soon as Duke hit the button.

"Is it a person?" Dick asked.

"No. Nineteen."

"A book?"

"Yes. Eighteen."

"A book you read recently?"

"Define recently."

"Uh, a month ago max."

"Then, no. Seventeen."

Dick hummed in thought. "Is it a mystery?"

"Shi--" and suddenly, as if Duke skipped to another point in a video, he heard Dick say "Is it _Death on the Nile?"_ and Duke blinked really hard after taking a good look at the clock timer and said, in the present moment, "It's _Death on the Nile,"_ a full twelve seconds before Jason would confirm it.

"Twelve seconds, this time," Duke said, and both of them looked at each other.

"Why was it faster for yours?" Dick asked. Jason shrugged.

"Maybe Duke just likes me more?"

"No comment," Duke said from the backseat.

Dick looked out the window and the still dormant warehouse they were nominally staking out.

"Okay, it looks like nobody's coming out anytime soon. Jason, switch seats with me."

"Why?" Jason asked, though he was already unbuckling his seatbelt. Duke surmised that being contrary was probably just in his nature.

"Well, either it was faster for you because there's some human component to Duke's powers, and they like you more, or it has something to do with our positions."

"I don't think it's a person-to-person thing," Duke said. "Doesn't make sense; my powers work fine on random goons."

"Physical distance then, maybe?" Jason said. "What if one of us got in the backseat with you?"

They ended up trying a few combinations, shuffling around in the car like they were playing musical chairs; Duke very much hoped that at least between the two of his foster siblings, someone was still keeping an eye on the warehouse.

A few combinations and a lot of trial and error later, with the aid of a tape measure that Dick just had in his pocket for some reason, the brothers had worked out a rough approximation of Duke's complicated relationship with linear time.

"I think it's the inverse square law," Dick said, looking at the brief table of numbers that they'd written up on the back of a receipt, because it isn't science unless you write it down.

"What?" Duke asked, scooting forward so he could lean between his brothers and get a better view.

"The further away, physically, from the event, the less into the future you can see, at an increasing rate. The seconds into the future aren't one over distance, it's one over distance squared."

"So," Jason said, "if I try to get up close and stab you, you'll see it coming from a minute away. Stand a foot away, and you'll see it, what, with fifteen seconds to spare? But if I'm six feet away, you'll only get a half-second warning. Less, probably."

"Please don't stab me at all," Duke said a little weakly.

"Don't worry about him," Dick said. "He acts tough, but he cries at the end of _Dead Poets Society_ every time."

"It's a good fucking movie," Jason muttered. "Anyways, maybe we should get you better long-distance combat training; you'll have the edge in hand to hand, but looks like your powers won't do much for a sniper."

"Also," Dick said, stretching in his seat a little, "looks like you're stuck staking out for hours like the rest of us mere mortals."

"Looks like," Duke said, holding on to the receipt. The numbers were scrawled down in Dick's handwriting, and he absentmindedly realized that Dick put lines between his 7's, just like Alfred, the few times Duke had seen the older man write down a grocery list. The way he did, too, because his dad had been the one to sit with him on his math homework, back in elementary school. His eyes tracked to where the little equation was circled, a preliminary _?_ underneath it, and wondered who exactly he'd inherited his powers from, what life his mother had lived before she had him.

He folded the receipt up carefully, smiling involuntarily as he saw the reverse side: a record of the swiss miss hot chocolate Dick must have run out and bought only a few hours ago before this stakeout.

"So I guess I-Spy is out of the running, then," Dick said.

"Why would we even play that? What is there to spy, other abandoned warehouses?"

"Well, I spy a stick in the mud."

"Very mature," Jason said, draining his drink and settling the cup in a holder. They settled into silence for a bit, before Duke, in a surge of confidence, broke it.

"You really like _Dead Poets Society_ that much?" he asked, a smile tugging at the side of his mouth.

"Not you too!" Jason exploded. Dick laughed, twisting to avoid Jason's flung out hands as he gestured and expounded: "It's a _good movie,_ Robin Williams is in it, and the last scene would make anyone cry. It'd make Black Mask cry. Shut up, Dick."

"I didn't say anything!"

"It's okay," Duke said, playing along. "But it's not even the best Robin Williams movie."

"Okay," Jason said. "Name a better one. I'm waiting."

"Good Will Hunting," Duke said, promptly. "Good Morning, Vietnam. Al--"

"Don't say Aladdin," Jason said, shaking his head.

"Night at the Museum," Dick added, which really tossed gasoline on the fire. Jason immediately whipped around to look at Duke.

"Please don't tell me you agree with that," he said, and Duke seesawed his hand and bobbed his head enough for Dick to claim victory. 

Their ensuing argument managed to go on for another half hour, nearly causing them to miss when four suspicious figures filed out from the warehouse, barrels in hand to be loaded into an idling truck. This, of course, led to one thrilling chase scene, which really consisted of running their marks down into the nearest alleyway, ineffectually interrogating four goons who didn't actually know anything about their mysterious employer, and then waiting around for the GCPD to get the message about an attempted robbery at Zimbardo and Fifth.

"Fucking _Night at the Museum_ ," Jason muttered into his comms while checking through the warehouse for more clues. Duke made eye contact with Dick and they both cracked up at the same time.

**Notes for the Chapter:**

> Pinning down a timeline for Duke is fairly hard since he's missing from a lot of tie-in events. Assume this is post- Batman and the Signal, but pre- Duke and Cass's current run on Outsiders.
> 
> Anyways, DC definitely contradicts me re: the science of this, I'm sure Duke's canonically seen ridiculously far into the future before from far away, but I thought it would be cool if Duke's future-vision was based on the nature of brightness and luminosity. The chapter title refers to the principle that apparent brightness (ie, light we see) is a function of the intrinsic luminosity (ie, the "real" brightness of an object) divided by 4π and distance squared. If you're curious, because I did actual math (okay, basic algebra) for this chapter, Duke's "future vision" equation is:
> 
> (time seen into the future, in seconds) = (15)/[(distance from Duke, in feet)^2]


	3. j*=σT^4

**Summary for the Chapter:**

> The Stefan–Boltzmann law states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time j* (also known as the black-body radiant emittance) is directly proportional to the fourth power of the black body's thermodynamic temperature T.

It was a bright, cold day in November, and Duke was getting his ass kicked at basketball.

"Alright, alright," Duke said, lining the ball up just right. He used to think he was good at this game. He turned around, closed his eyes, and launched the ball overhand, waiting for the telltale swish of the net.

"Boo!" Stephanie Brown heckled from the bleachers. He had thought she seemed like a nice girl when he had met her for the first time, a notion she had quickly disabused him of. "That's weak shit!"

His beloved sister, Cassandra, cackled and nodded from where she hung slightly off Steph's arm. Duke sighed as his sister bounced to her feet and resigned himself to getting another letter.

The girls both mimicked his shot perfectly with a nearly insulting level of perfunctoriness to their motions. Duke wondered again what spirit of bad decisions and humiliation had possessed him when Cass asked him if he wanted to play HORSE with two trained vigilantes. He was lucky that Steph and Cass had picked a random weekday afternoon to ditch college and homeschooling respectively; there were at least no civilian witnesses around to watch him get thoroughly trounced.

Cass grinned at him, cocking the ball against her hip as she examined the wide, empty court. Then she slowly started walking backwards.

"Don't do it," Duke said, shaking his head as she passed the free-throw line. Cass flashed him a smile that showed all of her teeth as she kept walking beyond it. "Don't do it, Cass."

"Can't keep up?" she asked, and Duke let his head fall back towards the sky.

"Man," he said, his competitive instincts flaring. Cass's smile got wider as she clearly saw his unspoken and unwilling rise to the challenge. "You know when you say it like that, I can't say no."

"Good," she said, finally, mercifully stopping at the half-court line. She tilted her head and pursed her lips in thought, her fingers casually tracing across the lines of the basketball. Duke knew this look. Cass's eyes were slowly tracking out her future motions, planning some kind of Olympic-level gymnastics routine on the fly.

"You realize," Duke said, leaning over to Steph, "whatever she does, you're gonna have to copy too."

"You don't think I can?" Steph asked, turning to face him with a flip of her hair and a cocked eyebrow, practically oozing confidence. It figured Cass's girlfriend would be just as self-assured and absolutely insane as she was.

"Gotta watch!" Cass called from way over at the half-court line. "'Else can't do it yourself!"

"Don't worry, Cassie," Steph called back, waving. "I could never take my eyes off you."

"Your girlfriend's a sap," Duke said, rolling his eyes.

"Steph, hit little brother for me," Cass said imperiously. Steph dutifully did so, punching him right in the bicep. "Now, watch."

Cass flung the ball up, striking a dancer's pose as she did so, before breaking into a triple handspring forward. She had timed it perfectly, the ball cresting and descending right as her legs came up on the third flip forward, sending it bouncing off in a perfect arc forward into the hoop. It didn't even scrape the rim, naturally.

Cass jumped back to her feet, her hands in the air, and then took a flourished and theatrical bow as Steph politely and enthusiastically golf-clapped. Duke shook his head.

"You guys suck," he said.

"Love us," Cass said, sticking her tongue out as she bounced off to retrieve the ball.

"I love you because I am legally your brother and I am therefore legally obligated to," Duke said. "There is no other reason for me to put up how much you guys suck."

"Li-aaaar," his sister said, sing-songing the word. 

"Nope," Duke said, sticking with it. "You guys are bullies. You guys are the worst. I'm chained by familial duty."

"Sore loser?" Steph asked, holding her hands out for Cass to chest pass the ball over.

"Oh, totally," Duke said. "I used to think I was good at trick shots."

Steph clapped his shoulder and shuffled to take Cass's spot on the half-court line. "You'll learn," she said.

Duke looked down to find his sister occupying the recently vacated space next to his left elbow. Cass looked up at him, an question in her smile.

"Do you like her?" Cass asked, gesturing ever so slightly with a nod of her head to where Steph was standing, a ways away, her sneakered foot on the ball as she paused to tie her long blonde hair back. Duke almost blinked; his sister seemed almost apprehensive of his answer, like she was genuinely worried he and Steph weren't getting along. 

"She seems nice," Duke said, and Cass smiled in a way that made her eyes close a little with the force of it, her freckled cheeks stretched.

"She is," his sister said. "Talks a lot, so I don't have to. Always understands me."

"Yeah?" Duke asked. "That why you always make the drive all the way to Bludhaven every Saturday? Wow, sounds like you simp-- ow!" 

Cass had managed to hit him right where Steph had as well. He might actually have a bruise tomorrow. He rubbed his arm and shook his head at Cass.

"Who even told you what that meant?"

"Tim," Cass said, holding her fist up threateningly under his nose. "Listen when big sister is bonding."

"Is that what this is?" Duke asked. Cass nodded, crossing her arms together over her chest as she raised her chin regally. "I thought you just wanted an excuse to kick my ass."

"That too," Cass admitted, unable to keep a straight face.

Duke shook his head, also struggling to keep his grin down. He looked over at Steph, who had finished tying her hair back into a tight bun and was now thoughtfully weighing the basketball from one hand to another.

"I guess Stephanie is pretty cool. You know, for an East End girl," Duke said.

"I heard that, you Narrows asshole," Steph called, looking still at the hoop and baseboard rather than them. Duke shook his head, finding himself ready to volly back all sorts of stock phrases from the dictionary of familiar neighborhood rivalry. He didn't get the chance, because that was when Steph, still studying the angles on the field, tossed her own ball up and threw herself forward into a handspring.

Steph stumbled a little more than Cass had, taking a little more time than his sister did when it came to chaining the handsprings together, but she had clearly accounted for that in the sharper angle at which she tossed the basketball. It gave her plenty of time to get to the end of the third handspring just in time to kick the ball like a human foosball, letting it arc fully into the hoop.

"Fuck yeah," Steph said, stumbling a little dizzily as she dusted herself off, but otherwise upright. "Physics."

Cass put her fingers between her lips and whistled in appreciation, to which Steph struck a triumphant pose as she jogged over to get the ball.

"Fuck yeah!" Cass echoed, and Duke did a double-take as a few things clicked into place.

"Is she the one who taught you how to swear?" he asked, pointing over at Steph.

Cass nodded. "I asked her why Alfred didn't let anyone say certain words."

"Why?" Steph asked as she jogged over. "Are they still blaming Jason?"

"Yep," Duke said.

"Oh, that's great," she said, cackling. "World's best detectives. You're up next."

Duke caught the ball with a fumble and jogged over to the half-court line, trying to remember the various strains of advice he'd been given. Dick had shown him how to tumble a few weeks ago, mostly as a technique to bleed off all the excess force from a fall at a height; it was Cass, however, who'd taught him how to break into a flip from a standing position.

He would be the first to say that he far preferred keeping his feet to the ground, happy to be the base for Cass's stunts, but that didn't mean he didn't know how to pull off a few tricks of his own.

Two handsprings in, he realized that he'd miscalculated slightly as he caught a glimpse of the ball coming down too long for one final front-flip. In the split second as his hands hit the ground on more time, he folded himself down into a front somersault instead and let that forward momentum carry him forward, just in time to get back upright on his feet, his arms stretched forward to spike the ball up into the hoop like a volleyball player.

The ball made it into the hoop and Duke turned triumphantly to his judges.

"Are you not amused?" He called, spreading his hands wide.

Steph leaned over to Cass, her arms crossed. "What do you think, does it count?"

Cass rubbed her chin in mock thought: a gesture she had accidentally picked up from when Bruce would do it in real. "Not exact copy," she said. "Don't think it should."

"You heard the lady," Steph said, spreading her hands in a what-can-you-do motion. "That's an S."

"You're killing me, Cassie," Duke said, shaking his head and smiling.

"Hey, Duke," Steph said, "you think you can try blindfolding one of us with your shadow powers? I think I could make it from the free-throw line without looking."

"Uh," Duke froze. Cass smiled encouragingly at him. "I guess I could try? I'm still pretty bad with the fine control."

Steph just bobbed her head to the side. "I trust you."

"You sure?" Duke asked, rolling his sleeves up. "Sometimes people can't talk when I do this. If anything goes wrong..."

"Well, I trust Cass to be able to see if I'm in pain or anything, and I trust you to stop if she tells you to," Steph said with a shrug, casually, like that wasn't a really big deal at all.

Duke glanced at Cass again before taking a deep breath and reaching one hand forward towards Steph's face.

"Is the pose necessary for your powers to work?" Steph asked, and Duke felt heat rush to his face as he dropped his hand. "Oh, sorry! I don't mean that in a rude way --"

"No, no, uh, I don't think -- I think you're right."

"Whatever's comfortable for you," Steph said, her palms up, placating.

To be very honest, Duke had just been taking his cues from memories of watching superheroes on TV, seeing Martian Manhunter or Starfire on blurry news footage. As he concentrated on the space right before Steph's face, he felt suddenly like he was holding a conversation while trying not to gesture. It was technically possible, sure, but it felt a little unnatural, a little stiff. His hands involuntarily twitched, piquing Cass's attention.

"How does it feel?" Cass asked. "When you move shadows like that?"

At this point, the black threads had woven them fully around Steph's vision. Duke watched as she tilted her head from side to side, the shadows moving with her.

"It's kind of like," Duke bit his lip as he tried to think of an explanation. "You know how it feels when you put your hand up to a hose, and you're trying to direct the spray?"

"Hard to direct?" Cass asked.

"Yeah," Duke said. "At least to hit small targets. Steph, can you hear us?"

Steph held up a thumbs-up, her other hand coming up into the black threads.

"Can you hear me? Man, this feels so weird, holy shit."

"Can hear you," Cass affirmed, stretching up to her tip toes to wave her hand in Steph's face. 

"See that?"

"See what? Oh, wow -- Duke, did you know your shadows are kinda warm?"

"What?"

"Here," Steph said, trailing one of her hands down Cass's shoulder and arm until she could grasp her palm and bring it up to her cheekbone. "Feel that?"

Cass tilted her head. "She's right," she said, letting her fingers flutter in and out of the block of shadow like she was sifting through sand. "It's warmer than air around it."

Duke furrowed his brow before cupping his own hands together, directing the shadows to pool in his palms. The space progressively darkened until he was holding his own handful of void and as he let it slip through his fingers, he felt it too: barely enough to note, but the shadow was just ever so lightly warmer than the brisk November air around them.

"Wait, wait," Steph said, clearly forgetting all about the game of HORSE. Duke couldn't blame her either: in the month since the touch of Ishmael was forcibly pressed into him, he hadn't really wanted to think too hard about how his powers had been "evolved," and this was all as new and revelatory to him as it was her.

"Okay, can you try getting it all on me? Just mummify me," Steph said.

"Is it safe?" Duke asked.

"We'll find out," she said. Cass shrugged, putting her hands on Steph's forearms, anchoring them together.

"Go for it," Cass said, and Duke did. They watched as the black crept down, bathing her entire frame in darkness.

There was silence for a bit before finally Steph disentangled her hands from Cass's and signed,  _ "I don't think you can hear me," _ with thickly shadowed limbs, at which point Duke decided to cut it short, letting the shadows recede again.

Steph's slightly flushed and grinning face melted back into view and she wasted no time.

"That was so cool!" she gushed. "Okay, okay, everywhere the shadows touched got just a little warmer. And I could still feel you, Cass, but I couldn't hear or see anything. Duke, holy shit, I think you're doing something to the light and sound energy, maybe converting it to heat."

"What?" Duke asked. He was pretty sure he was not quite following.

"I mean, it's obviously a pretty sloppy conversion because it wasn't that warm, but I bet if you concentrated all the energy you got from light in one place, you could probably heat something up? Like, for real, noticeably, heat something up. There's probably some kinda light energy to heat equation you're taking advantage of."

"Physics?" Duke asked, one eyebrow up. "Thought you were studying to be a doctor."

Steph shrugged. "My uncle's a mechanic. Taught me some of the basics when I was a kid."

"Her uncle is Kite-Man," Cass confided, and Steph groaned. 

"Don't tell him that!"

"What? Kite-Man's good at engineering. Flies with the kite. Would be a good teacher."

"Most people are not really fans of having C-list supervillain family," Steph said, sighing.

"Hey," Duke said, "if anyone would relate?"

"Yeah!" Cass said brightly. "Team… villain parents." She held her fist out for Duke to bump it.

"Team villain parents," he said, obliging his sister. They segued smoothly into their highly ritualized and completely pointless secret handshake, something they'd come up with while waiting around on some Outsiders mission or the other.

"Yeah, yeah," Steph said, "We all got bad bio dads. But only one of us got superpowers out of it."

"Are we sure Cass doesn't have any superpowers?" Duke grumbled. His sister grinned in the way she liked to do when she knew she was being annoying.

"He's just worried. Thinks powers are scary, doesn't like how he got them."

"Hey, no junior psychoanalysis," Duke protested. "Save it for Arkham."

"No, come on," Steph said, kneeling down and casting around for the backpack she'd brought with her. "Only way you ever stop being afraid of the unknown is to get familiar with it. Let's test this shadow theory." 

She came up triumphant with a paper cup of plain black coffee from the coffee shop across from the courts. It had mostly been drained already, only a mouthful of liquid left, and it had long since stopped steaming after exposure to the wintery air, having been set on the slushy, recently iced over pavement. Steph sat down cross-legged on the cement court, brushing aside some stray dirt so Cass could plot down next to her and look up expectantly at Duke.

Duke for his part sighed and sat down with a little trepidation, completing their little circle. He held his hand out for Steph to hand the cup over.

"Have at it," she said, relinquishing the cheap cup. Duke turned it over and over in his hands, watching as the few remaining ounces of deep brown liquid moved in small tidal waves in response, the silt of the improperly filtered coffee grounds shifting as he went.

He narrowed his eyes and concentrated really hard, half expecting nothing really to happen. The part of his brain that was permanently stuck at the whims of the push and pull of shadows perked up anyways, relishing the opportunity to direct all of that swirling chaotic energy onto just one target. Almost without him registering, the whole basketball court was beginning to darken like a sunset on triple speed, and the two girls looked around in curiosity. Duke concentrated further, unable to tell if the sensation of the cup beginning to heat against his fingers was just his brain playing tricks on him.

With a pop -- soft, like the sound of a lightbulb going out -- it was all over. Duke blinked back into the present, looking up at a courtyard that looked exactly as it had before like the encroaching shadows had been nothing but a figment of their collective imaginations. Except, as he tracked the line of sight of his sister and her girlfriend, he registered that the shops behind them used to have their lights on. He watched with furrowed brows as people suddenly streamed out of the doors of the sandwich shops and the laundromat, conferring with each other and pointing up at their lights, the ones that clearly were not working right about now. None of them, it seemed, noticed the three teenagers sitting around in the empty basketball court across the street.

"Did I--" Duke started to ask, before cutting off the stupid question.

"Well," Steph said, "I have a suspicion."

Cass, ignoring them both, reached over and plucked the forgotten cup of coffee from Duke's numb fingers. She took a delicate sip before nodding.

"Not cold. Kind of warm. Good job," she said, handing it off to Steph, who took it without looking, taking a sip with her eyes still fixed on the shops across the street and their unusual power outage.

With an electrical humming noise, the power came back in blinks to the neighborhood. They all collectively breathed a sigh of relief.

"Oh, thank god. I was not looking forward to telling Babs how we accidentally broke the Gotham power supply to get a lukewarm cup of coffee."

Then, Cass's phone went off and they all froze again.

"There's no way he knows," Duke said. "That would be--"

"He totally knows. With his creepy bat detective senses. He just sensed it was us."

Cass, meanwhile, had silently answered the call and pressed the phone to her ear. She listened with an uncharacteristically chastised expression for a few seconds, before suddenly looking up and making eye contact with Duke.

"Oh no," Duke said. "Please do not snitch. Cass. Please. I'll do your chores."

"He's with me," Cass confirmed, like a snitch, before holding the phone out for Duke to take. Duke looked at it like it was a venomous snake.

"Duke," Bruce's voice came from the phone. "I know you're there. Do you care to explain why a sizeable chunk of Midtown just lost power?"

Steph finally took pity on him, leaning in close to the phone and saying: "Don't blame him, it was our idea. Did you know his shadow powers are actually just him converting light energy away to heat?"

"Stephanie," Bruce said, sounding even more deeply tired than he had before. "Thank you, that is genuinely helpful information. Please refrain from blowing a power grid next time you want to conduct these impromptu tests. We have an entire lab in the Manor."

"Noted," Steph said.

"Give the phone to Duke now, please."

Duke sighed and took the phone, reluctantly taking it off speaker and holding it up to his ear.

"Converting light to heat?" Bruce asked.

"Yeah," Duke said. "Steph was the one who noticed first. It's barely there, honestly."

He motioned for the coffee and took the final sip, grimacing. It wasn't cold coffee anymore per se, but it certainly wasn't what anyone would consider particularly warm. Especially considering heating it up this marginal amount had taken out the power in nearby shops.

"Still," Bruce said. "I'm glad. I know this has been hard for you."

Duke swallowed, unable to even begin to think of a response for a second. He settled for a slightly strangled, "Yeah," because waking up with new meta powers from an evil dad he'd never met before was scary enough before his brother's crazy grandfather got someone to inject him and "evolve" him, and there was really no other way to summarize that.

"Don't let your sister talk you into anything else inadvisable," Bruce said, fondness in his tone. 

"Would never!" Cass called, somehow managing to overhear. She and Steph were smiling, leaning into each other in a way that somehow didn't make him feel like he was intruding.

"I think I'm good," Duke said, smiling back.

**Notes for the Chapter:**

> Technically, in physics, a black body is a very specific and idealized object, so this equation doesn't quite apply to just everything. However: hopefully there are no die-hard physicists in this audience to call me out on this, and it is still true that radiated energy is directly tied to heat, therefore, it does make sense for Duke's powers to have a heat component.
> 
> Also, this chapter is set mid- Batman and the Outsiders.


	4. A=ɛlc

**Summary for the Chapter:**

> Spectroscopy is the study of the interaction between matter and electromagnetic radiation as a function of the wavelength or frequency of the radiation.

It was almost a quiet day in the Manor, if one could ignore the sound of crashing and fighting downstairs. Which Duke was doing, naturally. 

The silent stillness of the mostly-empty house was only punctuated by bursts of violence once every few minutes, though the swearing had gotten louder at an exponential rate. It hadn't managed to get so loud that the individual words would filter up past three floors and two sets of closed doors, but based on pitch, Duke could confidently say that it was probably both Damian and Tim contributing to the cacophony of cursing.

No, he didn't know what they were doing. He had also very little desire to go downstairs and actually discover what could possibly get his two most antagonistic brothers -- he was including Jason "I was a drug lord once" Todd in that -- to willingly be in the same room as one another. He, a sane and well-adjusted person, was going to stay holed up in his room for the rest of this school holiday, balancing redux reactions exclusively on paper instead of taking part in what he thought might be the bomb-making going on downstairs.

Tim, who had finished high school in two years -- half because he was very smart and half because he just disliked high school so much that he wanted to get it over with as soon as possible -- didn't even really have an excuse to be at the Manor. Every day was a non-instructional day when you weren't in school anymore! But, regardless, Tim had decided to willingly spend his Wednesday not at work, but with their tiny, firmly-grounded assassin brother. Duke didn't understand it; even Bruce was currently at his day job right now, and Bruce would usually do anything he could to get out of having to be a functioning member of typical society.

Either way, this morning, Duke had spent as long as possible out in his Signal costume; while crime in Gotham had a preference for the witching hour, there was still plenty of robberies to break up in broad daylight. He did have to cut it all short after Condiment King doused him with a bottle of mustard midway through a convenience-store stick-up. Duke loved his city and all, but sometimes he kind of wished he lived somewhere where the petty criminals didn't have gimmicks too.

One very long hot shower later, which mostly involved some very harsh scrubbing of his suit until he had expunged the faint pungency of yellow mustard, Duke had finally settled down to work on his chemistry homework. Naturally, that was when the other inhabitants of the house woke up.

Duke cracked his neck, slamming his textbook shut in triumph. What absolutely nobody had warned him about being an on-call daytime vigilante was that when crime decided to strike in the middle of fourth period, answering the call would mean ditching class and having to catch up at home. He had no idea that there would be this much studying involved in superheroism.

He shuffled his papers, tucking them away neatly into a folder and dropping it into his backpack, out of sight and already completely out of his mind for the next eighteen hours. Then he reached into the space of his backpack and groaned as his fingers met nothing.

Unbidden, a flashback came to him: late last night, working through half his math problem set, leaving it on the kitchen island table to come back to in the morning.

The kitchen island which, judging by the voices emanating and rising in pitch, was currently the stage for another installment in the grand epic that was Tim and Damian's rivalry.

Duke sighed and tipped his head back, weighing his options. Meanwhile, the yelling definitely got a little louder in response. Something crashed -- probably a bowl, judging by the distinctive noise of a round object spinning rim over rim only to eventually settle with an almighty ringing.

A little pang of hunger reminded him that he'd just done a lot of cardio with no lunch, and he had to come down to eat at some point. That decided for him.

With a sigh, Duke ventured out of his room, shuffling down the wood floorboards, passing the open door to Tim's neat-freak clean room and the closed and locked door to Damian's. Duke had only glanced inside Damian's room once when his youngest foster brother had left it open briefly after being called to go to dinner. The brief impression was something uncomfortably impersonal for a preteen boy's room.

However, as Duke passed the shut door, he noticed a post-it note under the gap. Clearly the adhesive had given out from wherever it was stuck on the other side of the door; Duke took a brief second to pause and consider if this was a violation of Damian's privacy before he gave into his nosy instincts and kneeled down to pull it free. Flipping it over, he was met with an inked drawing of Titus, dated a few weeks ago in the corner. Duke smiled at the surprisingly childish scrawl that marked Damian's artist signature. He carefully put the post-it face down and tucked it back in place in roughly the same place it had been found.

Descending several sets of marble stairs -- complete with overwrought  _ Gone With The Wind _ banisters -- only brought him closer to the ground zero of whatever explosion was brewing. As he drew closer to the kitchen, the clarity of the argument came into sharper focus.

"Could you measure out more carefully next time!"

"I was careful -- you must have spilled some of it."

"Where? Please point to where you think  _ I _ spilled flour."

"Hey guys," Duke broke in, turning through the doorway before stopping short. "Woah."

At least four different bowls were overturned, and Duke was fairly sure that was a smashed bottle of vanilla extract he saw underneath the stove. There was salt spilled all over the counter, the container left on its side like the girl with the umbrella had had a few too many; meanwhile, Duke spied more varieties of chocolate chips than he had even known they came in, all in the sort of fancy brands that would call whatever they stocked at Whole Foods plebian.

Damian, with flour smeared on his chin and nose in a way that made him look disconcertingly like his age, blinked up at Duke from where he sat with his knee digging into Tim's back.

"Hello, Thomas."

"Hey," Tim said, still face down on the floor, waving. "What's up."

"Not…" Duke turned to look behind him, possibly for an explanation. "Where's your adult supervision?"

"I'm the adult," Tim said. It was not convincing.

"You are not an adult," Damian argued back. It looked like they were gearing up for another knock-down, drag-out argument, which Duke feared the kitchen probably couldn't take.

"I mean, where's Alfred?"

"Oh -- Damian, get off -- Alfred's at bridge club."

"What?" 

"Yeah, new thing he's been doing. Don't tell him about," Tim successfully bucked Damian and got to his feet, dusting himself off very ineffectually, "all of this."

"Uh," Duke said. He gestured to his own forehead. "You got something."

Tim reached up and felt for where either baking powder or baking soda had gotten into the roots of his hair.

"Stealing Todd's look?" Damian asked, crossing his arms and looking up at Tim with a scowl. Tim scowled back, going to the sink to wash his hair, which, while unsanitary, probably couldn't be much worse than the unmitigated disaster that they had made the kitchen into. Tim also flicked his wet hands at Damian, who cringed away, much like a startled cat.

"Cookies?" Duke asked, still unwilling to set foot into the kitchen. He'd just washed foodstuffs out of his hair and he was not looking for a round two. He did also spy his homework, rescued from the cataclysm and marooned on the other side of the kitchen from him.

"For Alfred," Damian said with the sort of preemptive defensiveness of someone who was anticipating being made fun of.

"His birthday coming up?" Duke asked, unwilling to touch that emotional minefield.

"Something like that," Tim said, glancing at Damian.

"It's in a week, but it is rare that there is an opportunity in the kitchen outside his supervision."

"You guys should have said something, I would have come down to help," Duke said, hoping they wouldn't actually take him up on his offer too often.

Tim sighed heavily. "Oh, there's definitely a spot for you if you still want to help," he said, gesturing to the war zone behind them.

They were not playing fair. What could he say? He wouldn't aid in crafting a heartfelt and home-baked expression of their love and thanks to the one man who managed to keep them all, Batman included, alive? He had math homework?

  
  
Duke wrote a brief and heartfelt eulogy to his clean state before he stepped across the threshold into the kitchen and immediately found his bare foot coated in white powders of various textures and consistencies.

"We have a broom or something, right?" he asked.

"I'll get it," Damian said in a surprisingly dutiful tone of voice. Duke watched him leave the kitchen in mute surprise.

"Every time he's caught fighting at school, his punishment is to help Alfred dust."

"Ah," Duke intoned in understanding. "What about you? What happened when you got in trouble?"

"Same thing," Tim said with a wry smile. "I usually got in trouble for ditching, not fighting, but Alfred's had the same disciplinary measures in place for two generations of superheroes."

"Ain't broke, don't fix it?" Duke asked, picking his way over to the various mixing bowls. He leaned over to inspect the conglomeration of half-melted butter and egg-with-eggshells that was congealing in one bowl. "You added sugar to this, right?"

"What?" Tim asked, turning around. "Isn't sugar a dry ingredient?"

Duke stared. "Man, have you ever baked cookies before?"

"No," Damian cut in, returning with a broom that was as tall as he was. "Food such as that did not befit an assassin of the League."

Duke stared a little longer before turning to Tim. "Okay, he's a baby assassin. What's your excuse?"

"Incompetence!" Damian yelled, attacking the salt spill with dustpan gusto. 

Tim rolled his eyes. "I don't know, it never came up."

"Do you at least have a recipe you're following?"

"Uh," Tim trailed off. "How hard could it be without one?"

Duke shook his head and tried to sort through the various paper bags of flour littering the counter: in addition to the whole wheat, enriched, self-rising, white, brown, and cake flours, Alfred apparently stocked some absolutely wild varieties. After pushing the almond, coconut, arrowroot, buckwheat, cassava, and tapioca flours to the side, Duke found himself staring at a bag of what proclaimed to be "coffee flour."

"Like, the drink?" he asked Tim, pointing at the name.

"I think so," Tim said, wiping down the counter.

"That definitely doesn't go in cookies. Where's the sugar?"

Damian frowned from where he was attempting to get an overly sticky glob of failed cookie dough off his fingers. "I think we used the last of it already."

"Check the pantry, there's probably another bag in there," Tim said. Damian gestured to his gloopy fingers, already destined to smear overly-buttered cookie dough all over whatever he touched next. Tim sighed.

"Duke, could you--"

"Already on it," Duke said, skirting around the kitchen island to the massive floor to ceiling shelves that made up the Manor's pantry. A solid two-thirds of the dark wood shelving was occupied by shelf-stable canned foods; Duke would joke about planning for the apocalypse, but he was fairly certain that was the actual logic behind it.

The final third, on its own, still housed more food than all five of his siblings and his father could eat in a month on the rare occasions that they were even all together at once. Duke's eyes were drawn to the conspicuous gap where Tim and Damian had clearly raided all the baking supplies, down at the lowest shelves. 

At the very bottom, sat on the floor itself were several steel drums full of various bulk goods. Duke pulled the closest few towards him with significant effort, huffing against the awkward leverage. 

He eased the lids off of each before blinking down at the three unlabeled tins full of white powders.

"Uh, guys," Duke asked. "Which one's sugar?"

He felt a little hesitant to poke any of them, let alone put anything unknown in his mouth to check.

"Be careful!" Tim shouted over his shoulder. "One of those is arsenic."

"Arse--  _ what! _ " Duke felt very justified in dropping one of the lids and scrabbling away. "Why do you guys just have a can of arsenic?"

"We don't," Tim said. "Alfred does."

"It can be useful," Damian said, nodding gravely. "Arsenic is a superior poison. It has no taste, so it can be mixed with sugar and served in a victim's tea. A cumulative toxin, too, so a gradual poisoning could be achie--"

"It's a rat poison," Tim cut in.

"We don't have rats!" Duke said, still very horrified.

"That's because of the arsenic," Damian said. His face remained very grim and flour-streaked, and Duke had no idea if he was joking at all.

"Pennyworth certainly must have taken use of toxins at some point in his career; they would have been indispensable as a spy."

"I thought you said poison is the weapon of cowards?"

"That's only when you use it, Drake."

Duke let them squabble, assuming that they couldn't cause too much more damage than they already had. He drew closer to the tins -- or, as close as he dared, considering one of the tins was full of a poison -- and squinted.

The textures of each of the powders were subtly different, though they all winked in a crystalline fashion the way the dull white of the flours spilled on the counter hadn't. Speaking of the counter. Duke got up and swept a little of the salt into the palm of his hand and gave it a very close look, feeling the telltale way his vision would fuzz and the rest of the world would fall away when his powers started to engage, and he saw light in its interconnected webs and ebbs and flows--

"Are you okay?" Tim asked. Duke's head snapped up and he blinked, the world suddenly reasserting itself and clicking back into place.

"Yeah, fine," he said, shaking his head.

"Were you using your powers?" Damian asked, popping up at his elbow with no warning.

"Shit!" Duke swore in surprise, jerking so hard that he nearly sent the palmful of salt over his shoulder. "Don't do that!"

"Sorry," Damian said, unrepentant. "What were you looking at?"

"It's dumb," Duke said. Tim leaned forward in interest.

"Do you think you can see a difference in the color?"

"It's not--" Duke tilted his head, bringing the crystals up again. "I don't know if it's color or what, but I see something."

Tim and Damian exchanged glances. Duke wasn't sure if he should have felt apprehension or not, but he was primarily distracted by the way his vision resolved itself on the salt: it felt like he was peeling away films and films of tint until he got to the clear truth underneath it. The way individual strings of light came away in distorted waves.

He turned to the three tins and instinctively had to screw his eyes shut against the onslaught of pure color assaulting him. Slowly, he opened his eyes back up, letting his pupils acclimate. As the pure sensory overload slowly faded, he started to register the patterns in the distortion.

The can in the middle, whatever was in it, was doing the same thing to the light as the salt in his palm. With a glance back at the salt to confirm, Duke pointed at it.

"Salt," he said. "I think. Light comes off it different."

The tin on the right was much more muddled, complicated to Duke's eye the same way the metal of the tins was and the structure of the wood and the skin of his own palm. The left, on the other hand, was like the salt: crisp, obvious. Pure, almost.

Damian kneeled down next to Duke.

"What are you seeing?"

"Emission lines, I think," Duke said, leaning even closer in despite himself. If he just focused, disentangled… 

"There!" he said, triumphant. "That one, on the right, the substance is made of three elements. Left is just two."

"There's one way to find out for sure," Tim said.

"Wait! I'm not positive; please don't taste it," Duke said, turning around in such panic that his vision went back to normal.

"He meant the Hahnemann test," Damian said. "Arsenic trioxide and hydrogen sulfate with hydrochloric acid combine to create a yellow precipitate."

"Right," Duke said, sheepish. "I knew that."

"Wait here," Tim said, already half out the door. "I'm bringing back some stuff, just wait!"

"We just have that ready to go?" Duke asked, then answered his own question. "Of course we do."

Damian kept watching him carefully. "Do you think the emission lines look the same when it's dissolved into water?"

Duke didn't have a second to dissuade his twelve-year-old foster brother; Damian had already lept up to retrieve a cup and a spoon.

"You are washing that cup so well later," Duke said.

"Yes, yes," Damian dismissed a little too easily, considering they were talking about actual extremely lethal poisons. "Do pay a little attention. This could save your life someday."

"I don't think I've made the kind of enemies that'd poison me yet," Duke said, following the preteen with bemusion.

"Yet," Damian said crisply. He carefully stirred the arsenic into the water with the sort of precise motions that left Duke wondering questions to which he had no desire to learn the answers to. 

  
  
"Yeah, okay, someday we're gonna have an actual conversation about why our butler grandpa has arsenic in the kitchen."

  
  
"Some day. Here, look."

Duke took the thrust-out cup with a delicate grip before bouncing a little on his heels, trying to psych his vision back up to go back to the weird absorption and emission line world it had been earlier.

"Do you have to move to activate your powers? That could be a problem, should stealth be call-"

"No," Duke cut in, getting embarrassed. He reestablished his stance on the ground a little more firmly. "It's just a thing -- I'll stop."

"Hm," Damian intoned, and Duke had to swallow a smile at how obvious it was that he was trying to imitate Bruce. He looked down into the cup, hoping it'd hide how much he wanted to break out into a grin.

Again, the rest of the world slowly started to slip away in a manner that felt like it should have given him a headache; the phantom throbbing in his head was almost as bad as the real thing. Slowly, the arsenic in the cup resolved itself, distorted through the ribbons of water -- dihydrogen monoxide, technically. Duke squinted a little more.

"It  _ is _ different," he said, bringing the cup a little closer to his eyes. 

"It must be hydrogen bonds," Damian speculated, putting his face up close to Duke's own. Duke gently nudged him away, swirling the dregs of the arsenic that hadn't dissolved down at the bottom.

"The H-alpha emissions would be different," Tim said, out of breath from running up and down several sets of stairs. "Oh my god, this is incredible. Duke, do you know what this is?"

He held up a set of bags of white powder.

"Is that something illegal for private households to store?" Duke asked, already reaching for one of the bags. On its own, it was clearer to Duke that whatever was in it was all emitting just one uniform wavelength -- a pure element, then. 

"Pure potassium is fine," Tim waved off. "I brought pure metals, too!"

"Tt," Damian clicked his tongue against his teeth. "Why not recreate the Periodic Table while you're at it?"

"Oh, I wish we could. God, I am so jealous, I can't believe you're a walking spectroscope. It makes so much sense, I have no idea why we didn't see it earlier -- that must be why you saw different colors in white the other day too--"

"Drake! Be careful with the fluorine gas!"

  
  
Duke shook his head a little, clearly the ghost migraine from where it had settled behind his eyes.

"Here," he said to Tim, handing the bags back. "Sorry, I don't think I can hold the spectroscopy-vision too long."

"Oh, yeah, of course," Tim said, gathering all the bags back into his arms. He made a face and something about the way the older boy hunched a little in on himself had Duke backpeddling.

"I'm grateful for this, really," he said. "I'd be way more lost without you guys."

"We're always here for you," Tim said, elbowing Damian when he opened his mouth.

"Yes, Thomas. We are always -- Drake! -- always willing to aid you," Damian said. For all the elbowing, it was said with a surprisingly un-grudgingly.

"Thanks, little D," Duke said, and the angry cat was back.

_ "Grayson," _ Damian hissed. "Infernal nicknamer that he is."

"It's fine, baby bat," Tim said with a smile thrown Duke's way.

"Baby--" Damian screeched, and Duke all but dove for the scrappy little assassin child.

"Hey, we just finished cleaning up!"

"And I am holding highly reactive compounds," Tim said. "Much harder to clean up."

"How about we take five," Duke said, already knowing he'd have to take his referee role for the rest of the day, "Tim puts that stuff away, and I look up an actual recipe."

"Sounds good," Tim said. "I do have to check if you got the arsenic thing right, though."

"That's fine," Duke said, straightening up and letting go of Damian. "Damian and I can go mix the dry ingredients."

"Of which sugar is not one, Drake," Damian said, manner Pennyworth-dry.

"You didn't know that either!" Tim defended himself. "Neither of us knew that!"

"You guys are so hopeless," Duke said. "What were you even planning on doing if I hadn't come down?"

"Some more trials, some more errors," Tim said. "You know, the scientific method."

**Notes for the Chapter:**

> The way spectroscopy works is that light particles will hit atoms, exciting electrons. When the electrons go up and then down an energy level/electron shell, they also emit a specific "emission line," which is unique for every single element! This is one of the primary ways that astronomers can tell what elements stars are made of: also, obviously, you can use it on things here on earth.


	5. f1 • V1 + f2 • V2 = 0

**Summary for the Chapter:**

> In optics, chromatic aberration (CA), also called chromatic distortion and spherochromatism, is a failure of a lens to focus all colors to the same point.

There were many good things about living in Wayne Manor -- easy access to a cornucopia of breakfast foods, private bedrooms and bathrooms, very little chance of property crime, the whole shebang -- but the downside absolutely had to be how often Duke came downstairs to find someone totally new sitting at the breakfast island, waiting to be engaged in conversation Duke wasn't awake enough to be ready for.

"You don't even live here!" Duke protested. 

Steph snapped her gum. "You don't know that for sure. Your house is big; maybe I've been _Parasite_ -ing you assholes without anyone knowing."

"Already know what's in the basement," Cass said. "Bats."

Duke, nevertheless, was somehow not reassured. "Nobody could actually, you know, live in here without anyone knowing, right?" he asked Cass.

"Your dad is Batman," Stephanie said, peeling a banana.

"Exactly!" Duke said, eyes wide. "Our dad is Batman! I got adopted by a crazy person who has mortal enemies, Steph. Mortal enemies. They swore blood oaths and everything."

"If Batman never kills," Cass mused. "Don't have to worry about ghosts."

"Has anyone ever brought that up to Jason?" Steph mused.

"Brought what up to Jason?" Duke's older brother walked in, rumpled in a distinctive way that said he must have spent the night.

"Hey, Doctor Jason and Mister Hood, do you think you're haunted by the ghosts of the people you've killed?" Steph asked, tipping her chair back to rest on its two back legs.

"First of all, I don't have any more of a split vigilante personality than you guys, so that nickname makes zero sense," Jason said, grabbing an orange from the bowl, "and second, ghosts aren't real."

Everyone turned to look at him. Dick chose that moment to walk through the door to the kitchen as well, hair windswept and clothes unwrinkled -- he must have driven up from his apartment.

"Dude," Duke said. "You are a walking zombie."

"Also, you've met a ghost before," Dick said, brushing past the two girls on the counter on his way to the coffee machine, ruffling Cass's hair as he passed.

"Were you listening at the door?" Steph asked, suspiciously. "You guys are so weird."

"Nah," Dick said. "We've already had this argument."

"It's not an argument," Jason said. "I've _been_ dead. Ghosts are definitely not real."

"So have I," Dick said, saluting Jason with his now-full coffee mug. Jason pulled a face.

"You were dead for five minutes, top."

"Who's the ghost?" Steph asked, right when Duke said, "Have you been dead too?"

"Boston Brand," Dick answered Steph, right as Jason reiterated, "For five minutes!"

"Wait," Jason cut himself off. "Deadman's a ghost?"

"Have you all been dead?" Duke asked. Steph pursed her lips and wobbled her hand.

"His name is dead-man," Cass pointed out to Jason.

"Only for a bit, I mostly faked it," Steph said, turning to Duke and affecting a conspiratorial tone.

"Hey, same," Dick said. They high fived.

"Crazy people," Duke said. "I got adopted by crazy people. Crazy dead people."

"Deadman," Jason repeated. "Dead man. I hate that guy."

"Don't worry," Cass told Duke. " _I_ haven't been dead yet."

"You should lean into it," Steph advised. "Make it a whole thing. Half of Gotham already thinks you guys are vampires anyways."

"Not me," Duke said. "I actually go out in the sun sometimes."

"Tim could stand to learn," Dick said, his words a little too loud for the conversation clustered around the counters. The room turned around to watch a bleary Tim stumble into the kitchen.

"F'ck off," Tim muttered, shouldering past three people to get to the fruit bowl. "Where's th' gremlin?"

"Hasn't come down yet. Why?" Jason asked.

"His fault I had to spend last night chasing Killer Croc through the sewers. M'gonna get that little goblin."

"Are we doing something today?" Duke asked.

"Designated bonding day," Steph said.

"Then why's Jason here?" Duke asked. "No offense."

"None taken," Jason said. "Today's just family bonding with guns."

"Paintball," Cass cut in. "Fun."

"She just likes being the one to shoot Jason back," Tim said.

Cass nodded enthusiastically.

"And yet she's still my favorite sibling, how does that make you feel?"

"Oh no," Tim said drily. "My attempted murderer doesn't like me. How could I ever have guessed this. There were so few signs."

"Speaking of," Dick said, "think maybe it's time to wake up the other one."

Dick left to go retrieve the youngest and also, presumably, Bruce. In the lull of conversation, Duke found some bread to make toast on and waited for Jason to finish brewing himself a cup of tea; it was always best to wait for one of his family members to be fully caffeinated and awake before springing the dozen questions Duke always inevitably had after any sustained conversation.

"So," Duke said, sidling up to Jason in an incredibly unsubtle attempt at sounding casual. Jason raised an eyebrow. "Paintball?"

"Told you we'd be working on that sniper issue of yours."

"By shooting me?" Duke asked. "With paintballs?"

"Don't worry," Cass said. "You'll have a team."

"It's the real reason Bruce adopted a football team of orphans," Steph said. "So he can run shooting drills in two teams of four."

"If you have any complaints about anyone," Tim said gravely. "Now's the time to get revenge."

"You guys are really intense about paintball," Duke said. 

Cass shrugged. "Just want to shoot Jason for the… what is the word? Funny because it's not expected?"

"Irony," Steph supplied. Cass nodded decisively.

"Shoot Jason for irony."

"Thanks," Jason said, flatly. "Personally, I shoot Dick and Bruce each time, even when we're on the same team. Full _Count of Monte Christo_."

"I don't think that was the point of that book," Tim said.

"It was the most satisfying part of the book," Jason said.

Steph snapped her gum again. "This is a fascinating look into your psyche."

"Is this just a thing?" Duke asked. "The paintball drills, not psychoanalyzing Jason."

"Yeah," Tim said. "For those of us who can't see the future, it pays to have practice in simulated shootout situations."

"Is _that_ what Bruce told you is why we do it?" Jason asked. "It's 'cause he can't bring himself to have fun without any justification and then went and adopted a bunch of preteens. He just wants to have fun with his kids and doesn't know how to tell anyone that."

Duke paused, toast half-way to his mouth. "You know, most people in Gotham are just pants-shittingly scared of you guys."

"We know," said Jason.

"And you guys are all actually really lame."

"We know," said Tim.

"Not us," Steph said. "People love Batgirls. We're trending on Twitter."

"Does everyone still think you're a second Batgirl?" Tim asked.

"It's a branding issue. My people are sorting it out."

"I'm her people," Cass said with all seriousness.

"Yeah," Duke said. "People keep thinking _my_ codename is the Spoiler. I didn't catch on until the Riddler tried to get me to answer a question about spoiled milk."

"That's so unfair," Steph muttered. "I was here first. I should get to be the recipient of puns about spoiled milk."

"All yours," said Duke. "I had to take the longest shower of my life to get the smell out."

Something about the characteristic rhythm of Wayne Manor had, at this point, burrowed itself into Duke's subconsciousness. He had clearly been spending too much time with the others, because it didn't surprise him at all when Damian called out, interrupting the conversation with the flair for drama that Duke would have hypothesized was genetic if every other sibling wasn't a counterpoint.

"Pretenders! Romans! Countrymen! The fewer men, the greater the share of the honor," Damian announced, his voice echoing off the walls with Pennyworth-approved enunciation.

"That's not the right--"

"Drake, I'll kill you first."

Dick trooped in behind him, carrying a duffle bag over either shoulder. "Murder is explicitly not the point," Dick said, both absentmindedly and tiredly. Clearly, this was something he'd explained several times over. Probably ineffectively each time.

"Is that the bag of guns?" Jason asked.

"It's the bag of guns," Dick confirmed, plonking one down heavily on the kitchen countertop.

"Sweet," Steph said, leaning over to unzip one. "I call dibs on the paintball machine gun."

That kicked off an argument between her and the usual suspects, Damian and Jason, over who got to have the biggest gun. Cass shook her head at Duke, tilting her head over like she was saying "they're all idiots," with her face and Duke smirked, hoping it conveyed, "you're dating one of the idiots." Cass stuck her tongue out at him before turning her attention to the argument -- Damian had vaulted up to the countertop and was gesticulating, clearly aiming for the aura of a child-emperor addressing his subjects, and missing the mark, getting something closer to little kid on a stepstool. It did make Steph and Jason, both grown adults, still look a little dumb for arguing back with just as much zeal.

"So," Duke asked, tearing his eyes away, "No Bruce?"

Dick grinned down at him. "He broke his foot last night. He's gonna tell you it's because he was pursuing Ivy. It's really 'cause Harley tripped him over and they got away while he was trying to ignore the fact that he got smashed in the foot with a hammer."

"Are they still, you know, bad guys?"

"Unclear," Dick said. "He's definitely on bed rest for the rest of the week, though. Which means we're probably doing teams of three this time. How do you feel about being the wildcard?"

"The what? Bad. I feel bad. I don't want to be a wildcard."

Duke had no idea what that meant, but he suspected it was something absolutely insane, just based on statistics; usually, when he learned new information, it was crazy.

"Don't worry," Dick said, which made Duke much more worried. "It's usually the most fun position."

"Fun for you, or like, fun for a normal person?"

"Technically, you're the least normal of us all," Dick said. Damian shrieked a war cry and jumped on top of Jason's back, while Steph hunched protectively over the duffel bag of paintball guns. "Biologically speaking. For the given definition of normal."

"Jason," Duke said, each word a little emphatic, "is a zombie."

* * *

  
  


Tim and Damian, unfortunate for them, definitely had to be put on the same team, or Damian would spend the whole time seeking Tim out to riddle him with paintball bullets, and Tim would then spend the whole time trying to get some kind of revenge, and it would be a whole thing. Theoretically, forcing teamwork would at the very least curb the worst of that, but in Duke's opinion, if putting them on the same team was going to work in general, it probably already would have.

Cass had also been assigned to that team as insurance. Nobody was about to start infighting with Cass keeping watch. She was much too competitive and -- Damian could deny it all he wanted -- scary for either of the boys to actively try to sabotage their own chances. 

Duke watched Cass rap her knuckles over Damian's forehead and winced in sympathy. His sister tended to be a little more physical in her admonishments, and Damian had quite literally stepped a few toes out of the tree line, giving their position away. Luckily, he hadn't been hit in one of the parts of his bodysuit marked potentially lethal in bright yellow paint; a foot wound simply meant he had to comically hop on one foot for the rest of the game.

"Psst," Duke said, as loud as he dared. "Guys! Hey!"  
  
In unison, his three siblings snapped around, looking up to the branch that Duke was clinging to with all he had. Sue him; he was a child of the urban jungle, and the woody forest ringing the Manor grounds was deeply unfamiliar territory for him.

"Ow, shit-- Don't shoot!" Duke had lost his grip on both his paintball gun and his branch and scrambled inelegantly down to the ground, hitting the mulch with a heavy thud. He wheezed, vaguely thankful neither of his brothers took this opportunity to shoot him. The paintball pellets _hurt_.

"Truce?" He gasped out, holding his pinky out first.

"Why?" Cass asked, crossing her arms and tilting her chin up. Tim and Damian came up behind her to flank her. Duke wondered very briefly if they'd practiced that before dismissing the thought; of course they had.

"You guys need all the help you can get," Duke said. He debated on dusting off his pants -- there were several pine needles clinging to his knees, and it did not make him look like a particularly dignified negotiator -- before instead reaching his whole hand out. "Only one of us uses guns on a regular basis. Way I see it, Jason's priority number one for all of us: he has the most experience."

"So why not join their team?" Cass asked, ignoring Duke's proffered hand.

"Well, we're partners, aren't we?"

Cass let him sweat for another few seconds before uncrossing her arms. "Partners," she said, shaking his hand. Duke grinned, relieved, before scrambling to join them behind a bush, presumably out of range of the other team.

"What's your plan?" Tim asked.

"Uh," Duke said. "I thought you'd have one."

"The last time Drake faced down Todd, he was nearly skewered," Damian sniffed. "Unless our plan is to lay down and die, I wouldn't look to him."

"Hey, asshole, I don't see you with any ideas."

"Tim," Cass said. "You are arguing with a ten year old."

"What's the range on these?" Duke asked, grabbing for his dropped gun.

"100 feet," Tim said promptly. "We checked."

Duke did a rough calculation in his head before sucking his back teeth. "Okay, future vision doesn't go that far. I'd only get a thousandth of a second's warning if I even knew where to look."

Tim chewed his thumb, lost in thought.

"We know where they are," he said. "Very roughly. The angle of the bullets are consistent with a sniper's perch on the roof of Wayne Manor."

"But Wayne Manor is huge," Duke said. Tim nodded absentmindedly. "So the roof is huge."

"Can you zoom in?" Damian asked. "With your powers?"

"Can I -- why would I be able to _zoom in_?"

"None of your powers make sense! You can see different kinds of red!" Damian said. "Why wouldn't you be able to zoom in on things?"

"Because that's insane," Duke said, turning to Cass for backup. Cass just shrugged. "I don't have _cameras_ for eyes. I just have weird powers."

"You do," Tim said.

"Thanks," Duke said dryly.

"Weird powers over light," Tim continued. "You can distinguish wavelengths."

"We've been over this," Duke said.

"No, wait, I'm thinking," Tim said. "Our problem is a sniper."

As if to underscore this point, the area right above their heads crackled with a shot. Everyone was too well trained to jump, but the nervous glances they sent each other made it clear they all wanted to.

"Problem," Cass corrected, "is we aren't used to sniping back."

"What's the difference between aiming batarangs and aiming a gun?" Duke asked, absentmindedly fiddling with his own paintball gun. His fingers brushed over the top and suddenly it hit him.

"Exactly," Cass said, in that creepy telepathic way she had.

"The scope," Duke said, looking down. "It's a magnification lens," he said holding it up. He squeezed one eye shut to look down the barrel itself.

"But it's distorted," Tim said, watching Duke with wide owl eyes. "Because of longi-"

"Longitudinal chromatic aberration," Duke interrupted. Then he looked up. "Sorry, I just -- I've been looking some stuff up on my own. About light. And stuff."

"Todd can't shoot through the vegetation, can he?" Damian asked.

Distantly, they all heard the rapport of a gun fired.

"Ah shit," Tim muttered, pulling his arm away from a particularly thin patch in the bushes. "Guess that's answered." His right arm was dripping in red paint and, from the wince on his face, he'd been hit right over where his bruise had just finished healing. Uncanny aim, Jason had.

"Okay. We're cheating," Cass said decisively. "Duke, can you fix the lens?"

Duke examined his own gun's scope. "Chromatic aberration happens when wavelengths of a certain color focus at different points. Makes the whole image look blurry." He flexed his fingers and concentrated. "I think I can refocus all the light but I don't think I can make the shot."

Tim, Cass, and Damian all looked at each other. Briefly.

"I can," Cass concluded the nonverbal argument. "Sit," she said to Damian.

"What are you doing?" Damian protested, sitting anyways.

"Need place to rest gun," Cass clarified, nocking it against his shoulder and kneeling further behind him. "Don't move. Or breathe."

Tim snorted, clearly delighting in this opportunity to poke the bear without Damian being able to swat back. "You heard the lady."

"Tim, shut up. Stay on lookout," Cass ordered. 

"You heard the lady," Duke said. Cass took a break from carefully calibrating her gun to smirk at him, and Duke smirked back. They'd have fistbumped if it wouldn't have meant Cass would have to start all over again with the gun. 

"Okay," Duke said, bouncing a little on his toes and doing all sorts of unnecessary flourishes with his hands. "Tell me what's better, one or two."

"Has Cass ever even been to the eye doctor? Is this joke landing?" Tim asked. 

"Shhh," Cass said. "And no. What's an eye doctor?"

Duke paused, blinked, and resolved to ask later. The rest of his vision was kicking in, kaleidoscopic colors fractalling out. Carefully, he tried reaching out for one set.

"One?" he asked, gently trying to shape the whole thing. He left after echoes as he went, black voids where the light had originally occupied space. "Or two?"

"Two." 

"Alright," Duke said, slowly hooking a finger in the cone of light he'd made. He yanked. "In focus now?"

"Mm," Cass hummed. "Who do I go for first?"

Duke blinked the light out of his eyes, the rest of the world reasserting itself. 

"Go for Jason first," Tim said. "Headshot, make it clean."

"Is that the tactical decision," Damian asked, "or a personal one."

"Shh," Cass said. "No moving."

Tim leaned in very close to watch, and none of them dared breathe. Slowly, Cass adjusted the gun by infinitesimal intervals, before falling very still. Big-cat-stalking-its-prey still. Then, glacially, she put her finger on the trigger and squeezed off a shot.

The gun barked and almost immediately, they heard a shout of an aborted "OH FU-", muffled by distance.

Duke didn't give them a second to celebrate. With them all gathered together in a frozen tableau, it was simple to grab his own gun -- set down at his feet in easy reach -- and pull off a spray-and-pray of shots.

"Thomas!" Damian shrieked, forgoing all pretenses at stealth. Cass simply glared, sprayed with green paint bullets. Tim honestly looked a little impressed.

In the distance, they could also hear Steph loudly say, "Dead people don't talk!"

"Sorry guys," Duke shrugged. "Wild card, remember?"

Cass simply lifted a finger. "Will forgive you," she said. " _If_ you get Dick next."

"Aye, aye, captain," Duke said. Cass shook her head.

"Still mad at you."

"Still partners?" Duke asked, leaning against the nearest tree.

Cass sighed, aggrieved. "Still partners. Will be waiting inside with hot chocolate."

* * *

In a surprise turn of events, Steph got the drop on both Dick and Duke, crowning her the wild card winner. Duke protested to no avail, and they all trudged back inside the Manor, discarding bodysuits drenched in paint at the doorstep.

Cass greeted them with mugs all in hand.

"You left Tim and Damian alone together?" Dick asked, half older-sibling-conspiratorial and half genuinely worried. Cass raised an eyebrow.

"Jason's there too. They're ganging up on him."

"Smart," Dick grinned, grabbing the bright yellow mug from her. "Downright Machiavellian."

"Who?" Cass asked, turning to Steph. She grinned and swooped in, kissing Cass on the cheek. Duke groaned and theatrically averted his eyes.

"I'll explain later," Steph said, carefully liberating her own mug from Cass's crowded hands. "Made with Nutella?"

"Always," Cass smiled. Steph grinned before sliding past her into the foyer, immediately joining the suddenly cacophonous argument that had boiled up beyond them.

"Which ones mine?" Duke asked, looking at the two mugs left in Cass's hands. One was a simple black and yellow mug with the iconic Batman logo on it, the kind that you could get in any Goodwill or Walgreens at the checkout. Though, upon closer inspection, the logo was slightly off -- clearly, it was based on an older iteration. The other mug was emblazoned with the same sort of small water-damaged stickers that he swore he had seen on a thermos in a cupboard in Dick's apartment.

"Yours," Cass said, handing the Batman mug over. "Made with water, how you like it."

"What's with the stickers?" Duke asked, taking a cautious sip. Cass grinned.

"From the speech therapist. Gave me stickers after each session, didn't have anywhere else to stick them."

"Mystery solved," Duke said. He proffered his cup and grinned when Cass obliged, clinking the two together as they leaned against the doorway, letting all the chill air in.

"Good day, little brother?"

"Good day, big sister."


	6. 1+z= γ(1+v/c)

Duke had been awake for verging on forty-eight hours. Stressed for the back half of those. His hands had started shaking a few hours ago and it took conscious effort to get them to stop -- conscious effort he wasn't about to expend if it meant taking it away from the effort to find his family.

He'd gone over the facts a couple dozen times already but in the absence of any new information, he reviewed again. 

At a quarter past two in the morning the night before last, Tim reported Damian missing, somehow vanishing in the seconds that Tim had taken his eyes off the other. Twelve minutes after that, Tim himself stopped responding to comms. Dick had been in Bludhaven, but he continued answering calls and texts until 2:30. His bike was found right on the outskirts of Bludhaven, near the bridge that spanned the bay between the city to Gotham; it was unclear if Dick had parked the bike there or if it was dragged over later. 

Duke had been woken up by the time Tim disappeared off the comms, and he and Alfred spent a tense night down in the cave, desperately trying to find any of the boys or getting in contact with Jason, whom nobody had seen or heard from all night. Jason still hadn't surfaced. Duke very much hoped he was actually taken by whoever had taken the rest of his siblings, or he'd never forgive him for not responding after the fifteenth frantic text.

Most terrifying of all, Cass had been taken as well. She and Steph went dark last: Cass's last communication to the cave was 2:58. 

Something had taken his siblings but left Bruce unscathed. Whatever it was, it had left almost no clues. There were no fingerprints on Dick's bike. Security feeds were wiped at every single location. Tim hadn't even caught a glimpse of anything, and it had come near enough to him to grab Damian, barely a few feet away.

"Master Duke," Alfred's voice came at his elbow. "It would be futile to ask one of you to get some rest, wouldn't it?"

Bruce, clicking away at his computer, didn't acknowledge the barb. Duke ran his hand over his face, letting the warmth of his palm linger over his scratchy and tired eyes.

"Maybe," he said before taking a deep breath and opening his eyes, the map of Gotham he'd been staring at already so burnt into the back of his eyelids that it was hardly necessary for the visual aid to be placed. Still, the four spots of light glared balefully back at him.

Tim and Damian had been abducted twelve minutes apart and only a couple miles from each other, but Dick had gone dark fifteen minutes later -- and fifty miles away, on the other end of the bay. Unless their abductor had been breaking speed limits with reckless abandon, which the log of traffic cops that night did not support, this was almost certainly the work of an organization. More disquieting still, an organization that knew exactly where to find all of them. Only Duke was spared by virtue of working the day shift, and he was quickly yanked off that.

On the other end of the cave, Bruce suddenly stilled. Duke didn't register that the sound of the keyboard had suddenly stopped until he heard his foster father make the hum he translated to "I think I have something."

Then, Duke got out of his chair so fast it nearly was knocked over. He rushed over to the massive monitor, leaning over Bruce's shoulder to squint at the pop up in front.

"What do you have?" Duke asked, completely ignoring personal space.

"I don't know," Bruce said. "It's encrypted. Needs a password. I think it's from Jason."

"Lead with that, holy shit," Duke said, nearly shoving Bruce out of the way. "What's the password?"

Bruce shook his head. "I tried the usual combos, but none of them worked. He still hasn't answered any usual channels."

"How long will it take to decrypt this, then?" Duke asked. He was nearly vibrating out of his skin, the sheer relief of their first clue in two days warring with his renewed fear over the fact that they still didn't know what happened to Jason.

"It should be cracked in an hour," Bruce said, in the tone of voice that said for him that he was fully prepared to simply sit motionless in front of the screen until it was finished. Duke hesitated.

"Can I try a password?" He asked. "Will that do anything?"

Bruce gave him a long, measuring look. Duke tried very hard not to fidget.

"If you enter another password in and it's wrong, we'll be locked out. It'll increase the amount of time before the software can crack the encryption, possibly to three hours. Are you very sure about this password?"

Duke hesitated. Then, he nodded decisively. "I'm sure," he said.

Bruce moved to the side, freeing enough space for Duke to stand at the keyboard and, with shaking hands, key in: NightAtTheMuseum.

It worked. Duke exhaled, long and slow, and felt a little of the tension leave his posture, enough that he was somewhat worried his knees would give out.

"Good job," Bruce said, which was easily the most Twilight Zone thing about the whole night.

In front of them, the pop-up expanded out into a map of Gotham, a twinkling red light blaring from Midtown.

"It's Jason's current location," Bruce said, reclaiming his spot in front of the computer. Duke let him, stumbling back over to his right arm and mentally push-pointing in the other four spots where his siblings had been abducted.

"Gotham General Hospital," Duke said, the distinct desire to throw up clawing its way up his throat. His hands were still shaking. He had to tell himself to stop, to not think about it, to push down the memories of his parents with their mouths frozen in rictus grins and raw fear in their eyes -- at least, fear before they went empty for good.

"Are you okay?" Bruce asked, far more gently than he would have assumed. Duke wasn't in the mood to appreciate it.

"Do I look okay to you?" He asked. "That must be where whoever it is is keeping them."

"Duke-" Bruce started.

"If you say something about benching me, you know I'm just going to steal one of your cars and leave to help anyways," Duke said. 

They stared each other down. Duke would later deny the thrill of vindication when Bruce looked away, but he also had just gained a very good understanding of exactly why all his siblings were so dead set on disagreeing with him all the time.

"Get in the batmobile," Bruce grumbled, "and don't do anything impulsive."

"I'd never," Duke said, which was a bald-faced lie. Bruce shook his head and didn't respond, the tension seeping back into the clench of his jaw and the stiff posture of his shoulders. Duke got in the passenger seat, glancing back over his shoulder at the baleful red light blinking out from the labyrinthean tangle of Gotham Streets up on the monitor.

He wanted to tell them all:  _ We're coming _ . But it was only a one-way connection.

They were a block away when the world went red for Duke.

They were out of the car. Approaching the target location on foot. It was close to four in the morning -- minimum foot traffic. Downtown area. 

Bruce had been ahead by a few footsteps when Duke felt the shock first, like a railroad spike going full Phineas Gage through his head. Right between his eyes, burning out the full breadth of his vision. Red for all of it.

Duke dropped to his knees, clutching his head, hoping to dig the tips of his fingertips into the back of his skull in an effort to distribute the pain or keep his brain from leaking out through his nose through sheer force of pressure or whatever he thought he was going to do. It took maybe a couple seconds, total. 

He blinked back the explosion, letting his vision come back into focus. He was still kneeling, palms against the gritty Gotham streets, when he looked up and registered that he was alone again.

"Batman? What was that?" he called. Bruce wouldn't have abandoned him, not now and especially not when all of Duke's siblings were missing as well. "B!"

Duke pushed past his pounding headache to tap into his comm. "Agent A, what happened to B?"

"His communication system have just fallen off. Something must have broken it."

Duke scanned the area, bouncing from surface to surface, his breathing picking up in speed just a little. He tried to stop himself from hyperventilating, but it was getting a little hard.

"You can't tell where he is at all?" Duke asked. He hoped he was just imagining the squeak in his voice.

"I'm afraid I cannot," Alfred's calm voice came back through. 

"Shit," Duke said. He stumbled against the side of the concrete walls of the hospital, his head still pounding. "Shit, shit, shit. What about Hood's tracker?"

"Still within the hospital."

Duke took a few deep breaths, enough for the briney taste in his mouth to subside. He looked up at the sign, several stories up, block letters illuminated from within. 

"I'm gonna have to go in and get them, huh," Duke said.

"Signal," Alfred said. He trailed off midway through; Duke didn't notice, too busy trying to regulate his breathing. "It is very likely that the perimeter of the hospital is secured by an EMP field. The Red Hood's signal is protected by a Faraday Cage, but your communications are not."

"So," Duke said. "I'll be on my own, yeah?"

"It seems so," Alfred said.

"Then," Duke said, pushing off the wall. "I better not mess up, right? Don't want you waiting too long with no response."

"It would certainly be better for my poor heart."

"Don't worry," Duke said, heading for the entrance. "At least one of us have to be looking out for your health."

"I commend you for the thoughtfulness."

Duke stopped in front of the double doors.

"Bye, A," he said softly. Then he crossed the threshold. There was a sharp sting and then a buzzing noise that resolved itself into the faintest sound of tinnitus. Duke pulled his now useless comm out of his ear and dropped it into a pocket. 

"Cool," he said, surveying the completely dark lobby of the hospital. "This doesn't look like a slasher set-up at all."

Something down the hallway rattled. Duke swallowed very nervously, inching forward. Unusual disappearances, a flash of bright red light, and a hospital. Duke didn't have good experiences with hospitals as a general rule.

Still, he had no choice. He pushed past the doors barricading the lobby from the rest of the hospital, letting the dark fall away. His powers rendered each surface curiously flat, no highlights or drop shadows to give a sense of perspective, but it was better than blindly stumbling through the dark.

It also helped him notice a certain powder strewn across the ground in a distinctive trail. Duke knelt down and swiped at the fine white powder, so well-milled that he couldn't even feel the texture through his gloves. Or rather, ever so close to white that anyone else would have mistaken it for the same shade as the linoleum floor below. Anyone else but Duke; this was as blaring and easy to pick out as a stop sign for him.

Maybe Tim's obsession with those different white powders was useful. He had no doubt that this trail of highly unusual breadcrumbs -- or perhaps a string for a labyrinth -- was all Tim's idea. 

Duke cracked his head from side to side before walking the line, turning where it turned and following through the rooms it followed. All throughout, he felt tension gather between his shoulderblades at the eerie silence. He turned over that flash of red light, the sudden disappearance, the EMP at the doors, in his mind over and over again.

The only explanation had to be a meta-human, but that meant nothing without any other clues. Duke had no idea how he was supposed to fight something he didn't even understand.

He couldn't tell what it was that made him pause before yet another turn down yet another bland, beige, lookalike corridor. Maybe it was his powers, some kind of spidey-signal sense, or one of those detective instincts Bruce had tried to drill into him. Maybe it was just plain apprehension. Duke paused at the corner and before turning, he let the future come to him.

Immediately, the blinding pain and flash of red light overwhelmed him. He dropped to his knees again. Working on instinct, Duke flooded the hallway with shadow, the inky black pouring out of him like an inkwell.

Something violently flew over his head, right where he had been. Duke panted against the ground, turning back over his shoulder. Nothing. In either the darkness or beyond it.

Cautiously, he extended the shadows as far as he could make them go; instinctively, he felt that he'd be safer in them, and whoever was on the other side wouldn't come for him through the black. From somewhere else in the bowels of the building, he heard an angry shout. He didn't understand the language, but the intent was clear.

Slowly, Duke got back to his feet. He eased back, inching to the room where the trail ended. He reviewed the facts.

The doppler effect was the change of frequency in a wave in relation to its motion to the observer. Put plainly, when objects moved towards a viewer while emitting waves, those waves compressed. Duke's old high school physics class put the concept in sound waves, the frequency of a car horn or the blare of an ambulance as it rushed by -- sounds familiar to any Gotham kid -- but it was also a concept in astrophysics. Light could compress too, a redshift from objects big enough and luminous enough to change. 

Or, objects moving fast enough.

Redshift.

Duke scanned the area, but the speedster -- he was wracking his brain for which ones were active and also villanous -- must have disappeared to another part of the hospital. He drew closer to the door, noting the card-activated lock and rattling at the handle before banging the door, still nervous to draw this much noise and attention to himself when under threat by someone who he would never see coming. Rather, someone he couldn't quite figure out how to see coming.

"Are you guys in there?" Duke hissed against the door. It was thick. He tried again, thumping out  _ R-U-OK _ in morse code against the door. Someone thumped out  _ Y-E-S _ back, and each pound against the fake wood sent Duke's heart racing anew.

There was another shout, closer this time. 

"Fuck," Duke muttered, fist against the door. He leaned against it and let his future-vision engage one more time, waiting braced against the door for the splitting headache and the drench of his vision in red. The red-shift. The shadows remained over them all, though Duke was starting to feel the strain of keeping it all up, like a soreness making itself known in his back and a pulsing headache behind his eyes.

Then, like an arrow through the temple, Duke felt the red and threw himself to the side, seconds away from being pulzerized by the speedster who blew through his shadows. Duke held his breath, barely a few feet away from a tall, broad man in a ridiculous outfit. He held the advantage, so long as he didn't make a sound.

Sure enough, after a few seconds, the man blinked away, reappearing at the end of the hallway. Duke slowly moved to a different position, sweating in the muffled heat of his own shadows. The hospital was probably evacuated by now, judging by the empty halls Duke had passed through, so he didn't feel as bad as he probably should have about extending the shadows even further, shouldering the burning ache and tapping further into the building's power supply. 

Unlucky for him, this was a hospital. He'd need extra time to induce a power failure. 

"Hey man!" Duke shouted, stalling. "What's your name?"

His shadows had extended to the whole hallway and then some, and the man was clearly unwilling to try to navigate the entire length of the corridor in total blindness. Score one for him.

"I am Savitar," the man said, a strong Eastern European accent to his words. Bulgarian, or Yugoslavian? Duke couldn't quite place it. "The god of motion."

"I don't think that's right," Duke shouted back, backing up behind another corner. Speedsters had a hard time with turning, right? Should be even harder in the dark.

"You question my skills?" Savitar asked.

"Maybe your recollection of mythology," Duke ribbed back. No response. Everyone liked it when his siblings quipped, but when he did it? Tough crowd.

Duke's shadows receded back, following him slightly. Like fish to the bait, Savitar followed.

He sprung his trap, letting shadows crash down the hall and envelope the other man, who stood stock-still. That was the floodgates opening with a resounding crashing in Duke's own head. He didn't think he had it in him to do that one more time; luckily, it was all he needed. The generators in the hospital had had enough, sputtering and dying with that one last yank on their energy. 

The lock on the door, hooked into that same electronic system, broke open. That was his family taken care of. Now the villain.

"Hey," Duke rasped, talking past the shattering migraine taking up residence directly behind his eyes. He badly would like to lie down after this. "You know what Savitar was really the god of?"

He swayed forward, swallowing past the pulsing in his head. With a shaking hand, he went for the bat on his chest, smacking it until it turned on in a blinding display of light, made even more jarring with the sudden vanishing of the shadows.

"The sun," Duke finished, knocking Savitar's disoriented ass out with his escrima.

"Wow," someone rasped behind them both. "Good timing with the quips. You're a natural."

"Is'sat Dick?" Duke asked, stumbling against the wall yet again. He screwed his eyes shut in an effort to stop aggravating his sore head. "You all okay?"

"We're fine," Bruce's distinct deep voice, free of his characteristic Batman gravel, resonated down the hallway. Duke felt familiar arms wrap around him -- almost definitely Cass's. 

"You did good," she whispered in his ear. Duke smiled, even as he slumped against her, weighing her down.

"It w's like with the basketballs," he slurred. "All the lights. Y'helped."

"No," Cass said decisively, slinging one of his arms over her strong shoulders and pulling them both up. Duke could blearily make out the forms of his family, huddled around Savitar's prone and unconscious form. "This was all you."

*

*

*  
End

**Notes for the Chapter:**

> i wrote this chapter while fully cognizant of the fact that that's not how anything works at all and you know what? i had fun. thanks for reading!

**Author's Note:**

> batcest shippers dni
> 
> everyone else have a great day ♥️


End file.
